L carnitine side effects


Why do people take acetyl-l-carnitine?

People have tried to treat many health problems using ALC, including:

Alzheimer’s disease. Several studies show improvements or slower declines in mental ability in people with Alzheimer’s disease who took ALC.

High blood sugar. Research shows that people with prediabetes had some improvement in their blood sugar levels after taking ALC for 2 months.

Alcoholism . ALC may help reduce cravings in people who are alcoholic.

Depression . Research found that ALC treatment reduced symptoms of depression in older people. It also improved dysthymia, a milder form of depression, about as well as a common medication.

Fragile X syndrome. This is a genetic problem. ALC has been used to affect certain behaviors in boys with fragile X, such as their social skills and hyperactivity, but research is mixed as to whether it really helps or not.

Male infertility. Men taking ALC in some studies had better sperm movement.

Sciatica. Research has linked ALC with less pain or less intense pain in people with pain from sciatica.

Peyronie’s disease . This condition causes the penis to curve abnormally. In one study, men who took daily ALC for 3 months had less pain and curving of the penis. The problem also progressed less in the men taking ALC.

Supplement makers suggest varying amounts of this supplement for different purposes. Common dosages range from 1 to 3 grams daily, divided into several doses. But optimal doses have not been established for any condition. Quality and active ingredients in supplements may vary widely from maker to maker. This makes it difficult to establish a standard dose.

L-Carnitine – Is It Good or Bad for your Heart?

L-carnitine is an amino acid that performs three very important functions that enhance athletic performance:

  1. L-carnitine is THE nutrient, the “ferry” so to speak, that shuttles fatty acids from the blood into the mitochondria, the energy producing “furnaces” in the cells, so that the fatty acids can be used as energy. If you want to use fat as a fuel as efficiently and effectively as possible, you need l-carnitine.
  2. L-carnitine also helps improve endurance by inhibiting the build-up of lactic acid, one of the primary causes of fatigue.
  3. L-carnitine has also been shown to reduce the accumulation of metabolic wastes during exercise. This helps increase workload output during exercise and enhancing recovery post-exercise.

Essential for athletic performance, heart health, and more

L-carnitine is a natural substance found in food. However, it is not considered an essential nutrient because the body can make it from the amino acids lysine and methionine. L-carnitine is the nutrient that transports fatty acids to the mitochondria for use as a fuel source and research shows that muscle carnitine levels are rapidly depleted during exercise, even moderate exercise. A number of published studies on athletes have shown that l-carnitine supplementation supports exercise performance. Athletes need more carnitine than they are capable of producing endogenously (inside the body). L-carnitine may be particularly important during periods of intense exercise as it may help to reduce post-exercise lactic acid accumulation and may increase maximal work output. It may also preserve muscle glycogen levels during workouts. As reported in the majority of studies, an increase in maximal oxygen consumption and a lowering of the respiratory quotient indicate that dietary l-carnitine has the potential to stimulate lipid metabolism (e.g. the utilization of fatty acids for fuel). Treatment with l-carnitine has also been shown to induce a significant post-exercise decrease in plasma lactate, which is formed and used continuously under fully aerobic conditions. Data from preliminary studies have indicated that l-carnitine supplementation can attenuate the deleterious effects of hypoxic (low oxygen) training and speed up recovery from exercise stress. Recent data have indicated that l-carnitine plays a decisive role in the prevention of cellular damage and favorably affects recovery from exercise stress. Additionally, among its other benefits for brain, body composition, and mitochondrial health, l-carnitine is essential for normal heart function.

Recent study poses questions

Recently, there has been some negative press on l-carnitine in the news. In a nutshell, the results of this study, published online in the journal Nature Medicine, suggest that orally dosed l-carnitine is metabolized by intestinal bacteria to produce a substance called trimethylamine (TMA). TMA is possibly further metabolized into trimethylamine-N-oxide (TMAO). It is theorized that TMAO prevents of excess cholesterol from being excreted, thus allowing it to infiltrate artery walls, which is being studied as a possible culprit for increased risk of cardiovascular disease. Sounds a bit scary, doesn’t it? But does that mean that l-carnitine supplementation puts you at risk?

Let’s take a closer look at l-carnitine in general, and this recent study and its implications. First, however, it’s important to keep in mind the axiom, ‘If a little is good, a lot is not necessarily better.’ Even basic substances required for life can be overdosed or underdosed, contributing to harmful life-threatening consequences. For example:

  • Water depletion/dehydration can kill you, but too much water (“water Intoxication”) is also lethal.
  • Too little sodium is known as hyponatremia, a life-threatening emergency. Too much sodium results in hypernatremia, which also has potentially fatal consequences.
  • Too much sugar or carbohydrates has been associated with diabetic issues, yet when the blood glucose turnover is excessive, consuming carbohydrates during exercise is safe and recommended.

So what does this particular study mean for me?

While this study is certainly intriguing, it’s important to keep in mind that the study subjects (both humans and mice) were given “chronic” amounts of l-carnitine. While we do not know how much was given to these test subjects, previous research done on humans suggests that a very large amount of l-carnitine (6 grams total/day) is required for significant increases of plasma TMAO. Other dosages administered three times daily (a total of 0.0g, 1.5g, and 3g total per day) showed no change in plasma increases of TMAO. REFERENCE: Bain MA, Milne RW, Evans AM. J Clin Pharmacol. 2006 Oct;46(10):1163-70. Disposition and metabolite kinetics of oral L-carnitine in humans. Sansom Institute, School of Pharmacy and Medical Sciences, University of South Australia, Adelaide, SA 5000, Australia.


Athletes can safely consume l-carnitine in supplement form to justify replacement. If you are consuming supplemental l-carnitine, we recommend keeping your totals in the range of 2000 mg (2g) per day. A non-athlete who consumes large amounts of meats that contain l-carnitine does not need to supplement this substance. Animal meat not only generates bodily carnitine, it also generates a protein structure that drives weight gain, growth factors, and plaque formation. If not derived from naturally raised grass-fed animals, there are other harmful substances found in meats that over time may prove harmful to health. Overall, we recommend not overconsuming substances from the animal kingdom that drive cholesterol accumulation on artery walls.

L-carnitine in Hammer Nutrition products:

Mito Caps – 125 mg/capsule Perpetuem – 25 mg/scoop Perpetuem Solids – 6 mg/tablet Sustained Energy – 16.6 mg/scoop

L-carnitine levels in foods (per 100 grams)

  • Lamb – 190 mg
  • Beef – 94 – 145 mg
  • Pork – 28 mg
  • Poultry and Seafood – 1.6 – 6.4 mg

Acetyl L Carnitine Benefits: The Supplement That Burns Fat and Powers the Brain

  • Acetyl-L-carnitine (ALCAR) is a mitochondrial boosting supplement that improves mood, learning, and memory.
  • ALCAR also helps your muscle mitochondria burn fat, which can increase your endurance, give you an edge in the gym, and help you recover faster.
  • For nootropic benefits, take two grams of ALCAR a day.
  • For better endurance and faster recovery, take 2-3 grams of ALCAR a day — half before your workout and half afterward.

Acetyl-L-carnitine (ALCAR), is a powerful addition to your biohacking toolbox. This valuable little molecule has been a staple in the bodybuilding and brain-hacking communities for years now, thanks to its ability to help you lose weight and power up your brain. Read on to learn more about the benefits of acetyl-L-carnitine, plus side effects, safety and proper supplement dosage.

What is acetyl-L-carnitine?

Acetyl-L-carnitine is an amino acid naturally produced in your body to generate energy. It’s also found in animal protein — namely, red meats. Many people supplement with acetyl-L-carnitine, because of its potential benefits.

What are the benefits of ALCAR?

You can use ALCAR to enhance your mitochondrial function cognition, workouts, and more. ALCAR helps your mitochondria (the powerhouses of your cells) burn fat and create more energy — especially for your muscles and brain.

Acetyl-L-carnitine has two main benefits:

  • Boosts brain power: ALCAR is an anti-aging nootropic, or smart drug, meaning, it helps your brain perform better. The acetyl group on it lets it pass your blood-brain barrier and reach your brain and nerves, where it can improve your mood, learning, and memory.
  • Burns fat and builds muscle: ALCAR can give you an edge in the gym, too. It shuttles fuel (in the form of fatty acids) to your muscle mitochondria, which ramps up your energy production and can increase endurance. ALCAR also pushes your metabolism toward fat burning while you work out.

Here’s a closer look at how ALCAR works.

Acetyl-L-carnitine and weight loss: how it helps burn fat

When you take ALCAR, it turns into carnitine in your body, and if your insulin levels are low — for example, from eating a keto diet (like the Bulletproof Diet), doing intermittent fasting, working out intensely, or being in a calorie deficit — carnitine becomes very important for burning fat.

When your insulin is low, your mitochondria start turning to fat for fuel. They grab onto stored body fat (or fat you eat), break it down into fatty acids, and send the fatty acids to your mitochondria. Your mitochondria turn those fatty acids into ATP (energy) that powers your cells.

But fatty acids can’t get into your mitochondria alone. They use something called a carnitine shuttle. Basically, carnitine latches onto fatty acids and carries them into your mitochondria. It gives your mitochondria the raw materials to produce lots of energy and function at their best.

In other words, you need carnitine to metabolize fat. If you’re low on carnitine, fat can’t get into your mitochondria, and you struggle to use it for fuel. But with abundant carnitine, your fat metabolism works like a well-oiled machine. That’s where ALCAR supplements come in, and why they’re so popular with bodybuilders.

Acetyl-L-carnitine for mood, memory and cognitive decline

Acetyl-L-carnitine is a supplement form of L-carnitine that can pass your blood-brain barrier, giving it access to the dense collection of mitochondria in your brain, as well as to the mitochondria in the rest of your body. That explains why ALCAR is becoming so popular as a nootropic supplement (something that makes your brain work better).

Here’s what the research has to say about using ALCAR to make your brain work better:

  • More mental & physical energy: Older men and women who took ALCAR daily saw a significant boost to their physical and mental energy levels, as well as better overall cognitive ability.
  • Improves cognitive function: People with low carnitine levels see a major decrease in brain function. Taking ALCAR improves that brain function. A lot. In a recent study, 8 out of 14 participants reversed a diagnosis of dementia and returned to their full cognitive abilities after taking ALCAR daily.
  • Lowers inflammation: Acetyl-L-carnitine decreases inflammation in healthy adults. Part of it is because ALCAR increases glutathione, your body’s master antioxidant. Side note: glutathione is awesome for hacking hangovers. And, as it turns out, ALCAR decreases damage to brain cells after drinking, too.
  • Boosts circulation: In healthy adults, ALCAR increased circulation and nutrient-rich blood flow after a high-fat meal. Good blood flow is an essential part of muscle and brain function.
  • Improves focus: Acetyl-L-carnitine improves attention, both in kids with ADHD and adults who struggle with mental fatigue.

Who should use acetyl-L-carnitine as a nootropic?

It’s worth mentioning that, although a few of these studies are in healthy young adults, a lot of acetyl-L-carnitine research is in older people. It’s clear that ALCAR is great for anti-aging, but what if you’re young and thriving, and want an extra edge?

As is the case with many nootropics, ALCAR is popular in the brain-hacking world thanks to lots of individual reports about how much it helps cognition.This is one of those supplements that’s worth trying on your own, to see if you notice any benefit.

What about ALCAR for improving your workouts?

Acetyl-L-carnitine for exercise and recovery

ALCAR has been a staple of the bodybuilding community for years. It’s got some decent research to back it up:

  • Increases strength: Resistance-trained young men who took carnitine 90 minutes before intense exercise enjoyed a significant increase in power output, as well as lower lactate levels (lactate contributes to the burning feeling in your muscles).
  • Burns more fat: Young men who took carnitine burned more fat during moderate exercise, and their muscles produced more energy during intense exercise.
  • Boosts testosterone: Men who took acetyl-L-carnitine after lifting had more dense hormone receptors in their muscles, which may have improved their testosterone uptake. https://www.ncbi.nlm.nih.gov/pubmed/16826026 In other words, ALCAR doesn’t increase your testosterone; it makes you better at using the testosterone you have (Here’s how to increase your testosterone).
  • Speeds recovery: ALCAR can speed up recovery and decrease muscle inflammation after exercise, in both men and women.
  • Better insulin sensitivity: ALCAR improves insulin sensitivity in people who don’t process glucose well.
  • Builds muscle: ALCAR is a powerful anti-aging supplement if you’re older and want to build muscle. In older people, it decreases muscle fatigue and increases fat loss.
  • Reduces muscle fatigue: One study found that acetyl-L-carnitine decreases muscle fatigue in young people, too.

Summing up: ALCAR can help you work harder in the gym and recover faster. And if you’re older, acetyl-L-carnitine is especially useful for maintaining your energy levels and shedding body fat.

Dosage: How much acetyl-L-carnitine should you take?

Acetyl-L-carnitine is a valuable addition to your daily supplement routine, especially if you’re an athlete or you’re looking for anti-aging benefits. As with most supplements, timing matters. Here’s what you need to know.

Most of the studies you just read about used between 1-3 grams of L-carnitine, taken every day. One gram a day seems to be a good place to start. From there, you can increase or decrease the dose as you see fit. Here are sample plans for taking ALCAR:

Acetyl-L-carnitine for nootropic benefits/anti-aging:

2g/day; half first thing in the morning, half in the afternoon

Acetyl-L-carnitine for fitness and fat-burning:

2-3g day; half 90 minutes before exercise (to increase your muscle endurance), half after exercise (to speed up recovery)

Acetyl-L-carnitine side effects and precautions

While ALCAR is generally considered safe for most people, you could experience some side effects, including upset stomach, nausea, vomiting, headache, dry mouth, and restlessness.

  • Consult your physician before starting any new supplement, especially if you’re pregnant, breastfeeding, or have a serious medical condition.
  • Acetyl-L-carnitine may interfere with thyroid function, and is best avoided if you have an underactive thyroid.
  • People with a history of seizures may also want to steer clear of ALCAR.
  • Do not use acetyl-L-carnitine if you’re taking blood-thinning medication.

Have you had success with ALCAR? Is it part of your go-to nootropic stack? Do you find it doesn’t work? Any benefits this article doesn’t mention? Leave your thoughts in the comments. And if you liked this article, be sure you subscribe below. You’ll get valuable tips about biohacking and becoming superhuman, delivered right to your inbox. Thanks for reading.

Join over 1 million fans

Sign-up for the Bulletproof mailing list and receive the latest news and updates!

  • Your Expert Guide To L-Carnitine

    When taken correctly, L-carnitine can boost both your training and your physique. In the gym, it can mean more endurance and bigger pumps. In the mirror, picture more muscle and less fat. And despite what you may have read, it’s safe.

    Don’t fear L-carnitine. Learn how it works and how to use it, and it can be a great tool to have in your arsenal.

    While it is often categorized as an amino acid, L-carnitine isn’t technically an amino. It is considered a “vitamin-like” and “amino-acid-like” compound that is related to the B vitamins. When it was first studied back in the 1950s, L-carnitine was referred to as vitamin BT.

    L-carnitine is formed in the liver and kidneys from the amino acids lysine and methionine. However, it is stored elsewhere in the body, primarily in muscle (including the heart), the brain, and even in sperm. In the diet, it mainly comes from meat and other animal products. You can get some from plant products like avocado and soybeans, but as a rule, meat is the best source—and the redder the better.

    Carnitine exists in two forms: D-carnitine and L-carnitine. The L-form is the kind of carnitine found in nature and is biologically active. On labels, you’ll see it listed as L-carnitine, L-carnitine L-tartrate, or Propionyl-L-carnitine. They’re all similar, and similarly effective. The D form of carnitine, on the other hand, is biologically inactive and isn’t sold as a supplement.

    Acetyl L-carnitine, also known as acetylcarnitine or ALCAR, is another popular supplemental form of carnitine. It can be found throughout the central nervous system, where it plays a role in producing energy and produces the important neurotransmitter acetylcholine.

    The acetyl group attached to the carnitine molecule enhances its ability to pass across the blood-brain barrier and enter the brain, where it acts as a powerful antioxidant. For this reason, some research suggests that acetyl L-carnitine may provide protective actions against aging processes and neurodegeneration.

    What does L-Carntine do?

    L-carnitine helps to transport fat, particularly long-chain fatty acids, into the mitochondria of cells. Once there, the fatty acids can be oxidized—used as fuel—to generate adenosine triphosphate, or ATP. L-carnitine does this cellular work both when you exercise and rest, but research confirms that it is especially effective during intense exercise.

    Without adequate carnitine, most dietary fats can’t get into the mitochondria and be burned for fuel. But for people with carnitine deficiency, it is a serious medical condition. It can lead to muscle weakness, stunted growth, an enlarged liver, and a number of other problems. This is one reason it’s considered a “conditionally essential” nutrient: Your body produces it, but if it doesn’t produce enough, your health can be seriously impacted.

    A study out of Scotland concluded that in addition to its fat-transporting work, L-carnitine also enhances insulin’s actions on muscle cells. What this means is that it can help keep blood glucose levels low, even after a carb-rich meal, while also aiding glycogen repletion. This is one reason I advocate taking this supplement with a post-workout meal.

    Some of the most interesting research into L-carnitine supplementation focuses on how it can enhance athletic performance.

    What are the Performance and Physique Applications Of L-Carnitine?

    L-carnitine’s bona fide role as a fat-burning supplement is well established. During bulking periods, it can help limit fat gains and make a “cleaner” bulk. If you’re cutting, it can help transport the fat you have into your cellular furnaces to get burned as energy.

    Burning fat as fuel: Some of the most interesting recent research into L-carnitine supplementation focuses on how it can enhance athletic performance. In one study, University of Nottingham Medical School researchers had one group of athletes consume 2 grams of L-carnitine along with 80 grams of a high-glycemic carb first thing in the morning and four hours later for 24 weeks. Another group only took the carbs.

    The researchers found that during low-intensity cycling, the subjects taking carnitine burned 55 percent less muscle glycogen while increasing the body’s ability to burn fat by 55 percent. During high-intensity cycling, the subjects taking L-carnitine had lower levels of lactic acid and higher levels of creatine phosphate, one of the primary building blocks of ATP.

    Fatigue resistance: When the Nottingham researchers measured the subjects’ ability to resist fatigue during a cycling test, they found that subjects taking the supplement were able to go more than 25 percent longer. This was likely because they burned more fat while preserving muscle glycogen, in addition to having lower levels of lactic acid and higher levels of creatine phosphate.

    Decreased Muscle Soreness, Improved Recovery: In a number of studies on human subjects, L-carnitine doses of just 1-2 grams per day have been shown to significantly reduce muscle damage from strenuous exercise, and improved recovery to exercise. It has also been shown to decrease muscle soreness. The best part? It wasn’t rats doing these workouts. It was healthy, active men and women.

    Better blood flow and pumps: This supplement’s performance benefits not only stem from its ability to increase fat burning and decrease glycogen use, but also from the way it can enhance blood flow to the muscles. Increased blood flow means more nutrients and hormones go where they’re needed most during exercise.

    How does this work? For one, carnitine reduces oxidative damage in the body’s nitric oxide (NO). But it also enhances the activity of a key enzyme involved in your body’s NO production. The net result is higher NO blood levels, which not only enhance energy during workouts, but also muscle recovery following workouts.

    Are There Side Effects to L-Carnitine Supplementation?

    There are few negative side effects from this supplement at reasonable doses. It can cause nausea, abdominal cramps, vomiting, and diarrhea when taken in high doses. Rare side effects can include muscle weakness in uremic patients and seizures in people with seizure disorders.

    How Should I Stack L-Carnitine?

    Quite simply, take it with carbs. Some early studies showed no benefit of carnitine because they failed to adequately raise muscle carnitine levels. This was because the supplement wasn’t taken at the right time, when insulin would be spiked and muscle uptake would be adequate.

    Newer research shows that insulin levels must be quite high for adequate amounts of L-carnitine to enter muscle cells, where it performs the majority of its work. On the flipside, taking L-carnitine enhances insulin’s actions at the muscle cells, helping to deliver more glucose into the muscle cells as well as more L-carnitine.

    While as little as 1 gram of L-carnitine can be effective, your best bet is to take 2-3 grams per dose for maximum benefit, along with at least 30-40 grams of carbs and 20-40 grams of protein, preferably with a meal. This applies if you take straight-up L-carnitine, L-carnitine L-tartrate, or propionyl-L-carnitine.

    Acetyl L-carnitine, however, is more easily taken up by the intestines and the muscle cells, not to mention the brain, in the absence of food. Therefore, this form of carnitine may be stacked with other ingredients that enhance fat-burning, such as caffeine and green tea, and taken between meals.

    Should I Cycle L-Carnitine?

    At this time, it appears that there is no need to cycle L-carnitine. Taken regularly, it should continue to be effective long term.

    When Should I Take L-Carnitine?

    One of the best times to take L-carnitine is post-workout, but you can take it with any other high-carb, high-protein meal throughout the day. If you want to stack carnitine with other fat-burning ingredients between meals, consider using the acetyl L-carnitine form.

    One strategy I found to work well for both fat loss and performance is to take 2-3 doses of acetyl L-carnitine with other fat-burning ingredients without food between meals, and to take 1 dose of L-carnitine or L-carnitine L-tartrate with a post-workout meal.

    You can take it with any other high-carb, high-protein meal throughout the day.

    Supplements like carnitine can help with body composition, but to see dramatic results you need to have your diet and workout program locked down. Take care of both with Jim Stoppani’s Shortcut to Size on Bodybuilding.com BodyFit Elite.

    L-Carnitine Side Effects

    Generic Name: levocarnitine

    Medically reviewed by Drugs.com. Last updated on Jan 12, 2019.

    • Overview
    • Side Effects
    • Dosage
    • Professional
    • Interactions
    • More

    Note: This document contains side effect information about levocarnitine. Some of the dosage forms listed on this page may not apply to the brand name L-Carnitine.

    For the Consumer

    Applies to levocarnitine: capsule, solution, tablet

    Along with its needed effects, levocarnitine (the active ingredient contained in L-Carnitine) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

    Check with your doctor as soon as possible if any of the following side effects occur while taking levocarnitine:

    More common

    • High blood pressure

    Less common

    • Fast heartbeat
    • fever


    • Seizures

    Some side effects of levocarnitine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

    More common

    • Abdominal or stomach cramps
    • diarrhea
    • headache
    • nausea or vomiting

    Less common

    • Abdominal discomfort
    • body odor
    • depression
    • dizziness
    • impaired vision
    • loss of appetite or weight
    • swelling in hands, lower legs, and feet
    • tingling sensation
    • weakness

    For Healthcare Professionals

    Applies to levocarnitine: injectable solution, oral capsule, oral solution, oral tablet


    Very common (10% or more): Diarrhea (35%), abdominal pain (21%), vomiting (21%), nausea (12%)

    Common (1% to 10%): Constipation, dyspepsia, gastrointestinal disorder, melena

    Very rare (less than 0.01%): Abdominal cramps

    Nervous system

    Very common (10% or more): Headache (37%), dizziness (18%), paresthesia (12%)

    Common (1% to 10%): Hypertonia, vertigo, taste perversion

    Frequency not reported: Seizures (with or without pre-existing seizure activity), increase in seizure frequency and/or severity


    There are reports from clinical trials of significant hypertriglyceridemia associated with high doses of levocarnitine (the active ingredient contained in L-Carnitine) (3 g/day) given to uremic dialysis patients.

    Very common (10% or more): Hypercalcemia (15%), hypervolemia (12%)

    Common (1% to 10%): Anorexia, hyperkalemia


    Very common (10% or more): Pain (35%), flu syndrome (29%), chest pain (15%), accidental injury (12%), asthenia (12%), fever (12%)

    Common (1% to 10%): Peripheral edema, weight decrease, weight increase

    Very rare (less than 0.01%): Body odor, International Normalized Ratio (INR) increased


    Very common (10% or more): Injection site reaction (38%)


    Musculoskeletal side effects, in chronic hemodialysis patients, for levocarnitine (the active ingredient contained in L-Carnitine) in relation to placebo therapy have included asthenia (8% to 12% vs 8%) and leg cramps (4% to 8% vs 13%). Mild myasthenia has occurred in uremic patients receiving D,L-carnitine (but not levocarnitine).


    There have been reports from clinical trials of significant increases in platelet aggregation associated with high doses of levocarnitine (the active ingredient contained in L-Carnitine) (3 g/day) given to hemodialysis patients.

    Very common (10% or more): Anemia (12%)


    Common (1% to 10%): Kidney failure (chronic hemodialysis patients)


    Common (1% to 10%): Parathyroid disorder


    Very common (10% or more): Pharyngitis (27%), cough increase (18%), dyspnea (11%), rhinitis (11%)

    Common (1% to 10%): Bronchitis, sinusitis


    Common (1% to 10%): Pruritus, rash


    Common (1% to 10%): Amblyopia, eye disorder


    Common (1% to 10%): Urinary tract infection


    Very common (10% or more): Hypertension (21%), hypotension (19%)


    Common (1% to 10%): Allergic reaction


    Common (1% to 10%): Depression, anxiety, drug dependence, insomnia


    Very common (10% or more): Infection (24%)

    1. “Product Information. LevOCARNitine (levOCARNitine (levocarnitine)).” Hi-Tech Pharmacal Company Inc, Amityville, NY.

    2. “Product Information. Carnitor (levocarnitine).” Sigma-Tau Pharmaceuticals, Gaitherburg, MD.

    3. “Product Information. Carnitor (levocarnitine)” Sigma-Tau Pharmaceuticals Inc, Gaithersburg, MD.

    4. Golper TA, Wolfson M, Ahmad S, Hirschberg R, Kurtin P, Katz LA, Nicora R, Ashbrook D, Kopple JD “Multicenter trial of L-carnitine in maintenance hemodialysis patients. I. Carnitine concentrations and lipid effects.” Kidney Int 38 (1990): 904-11

    5. Weschler A, Aviram M, Levin M, Better OS, Brook JG “High dose of L-carnitine increases platelet aggregation and plasma triglyceride levels in uremic patients on hemodialysis.” Nephron 38 (1984): 120-4

    Further information

    Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

    Some side effects may not be reported. You may report them to the FDA.

    Medical Disclaimer

    More about L-Carnitine (levocarnitine)

    • During Pregnancy or Breastfeeding
    • Dosage Information
    • Drug Interactions
    • Compare Alternatives
    • En Español
    • 3 Reviews
    • Drug class: nutraceutical products

    Consumer resources

    • L-Carnitine
    • Carnitine (Advanced Reading)

    Other brands: Carnitor, Carnitor SF

    Professional resources

    • L-carnitine (Advanced Reading)
    • … +2 more

    Related treatment guides

    • Peripheral Neuropathy
    • Carnitine Deficiency

    People use carnitine as an energy booster, antioxidant, and to support mood and cognition. Is the evidence there to support these uses? Read on to discover more about the health effects and side effects of carnitine.

    What is Carnitine?


    Carnitine is an amino acid found in nearly every cell of the body. It is a generic name for a variety of compounds such as L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine. The three are chemically similar and some of their benefits overlap. However, they have some distinct mechanisms of action and uses.

    • Acetyl-L-carnitine is generally used to improve brain functioning and cognition .
    • L-carnitine is used to increase energy levels and physical performance .
    • Propionyl-L-carnitine is used to boost circulation .

    Scientists think that all forms of carnitine play a vital role in the production of energy. Carnitine is said to help turn body fat into energy. It might also get rid of toxic compounds from the mitochondria to prevent their buildup. Carnitine is produced by the liver and kidneys and stored in muscle, brain, and heart tissue – all of which use fatty acids as energy .

    You’ll get carnitine from meat, fish, poultry, and milk. People with genetic disorders, chronic diseases, and those on a vegetarian diet can often benefit from supplemental carnitine. The same is true for underweight and premature babies. Other conditions that cause carnitine deficiency include angina (chest pain) and intermittent claudication (cramping leg pain from blocked arteries) .

    The FDA has approved the use of L-carnitine (by mouth or intravenously) treating L-carnitine deficiency caused by certain genetic diseases, end-stage kidney disease, and other disorders. It’s known under the brand name Carnitor.

    However, other medical uses of carnitine supplements have not been approved by the FDA. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.



    • Effective for L-carnitine deficiency
    • Supports mitochondrial health and energy function
    • Allegedly supports liver and brain health
    • May improve PCOS in women and semen quality and fertility in men


    • Many popular uses are not supported by evidence
    • May contribute to heart disease by metabolizing TMAO
    • Can cause nausea or stomach upset
    • Long-term use may cause oxidative stress in the liver and blood
    • Affects thyroid function

    Health Benefits of Carnitine

    Effective for:

    L-Carnitine Deficiency (Genetic)

    Oral and intravenous L-carnitine is effective for the treatment of primary and secondary L-carnitine deficiency due to inborn errors of metabolism (genetic).

    Likely Effective for:

    L-Carnitine Deficiency in Kidney Disease

    Dialysis reduces carnitine levels in people with end-stage kidney disease. The FDA has approved intravenous (by IV) L-carnitine for treating and preventing L-carnitine deficiency in these patients.

    Despite being FDA-approved for this indication, some studies have had mixed results. Evidence suggests that l-carnitine improves anemia and inflammation in people with this condition. However, it does not seem to affect the patients’ quality of life, muscle cramping, low blood pressure, breathing, or exercise performance .

    Carnitine taken by mouth is not approved for carnitine deficiency in kidney patients undergoing dialysis.

    Possibly Effective for:

    Chest Pain from Heart Disease (Angina)

    Evidence suggests that taking carnitine by mouth or intravenously may improve exercise tolerance in people with chronic stable angina. As an add-on to conventional therapy, l-carnitine may also reduce the frequency of chest pain (angina) in people with angina (microvascular type) .

    Scientists think carnitine and its derivatives may protect heart function by increasing glucose metabolism, increasing blood flow, correcting abnormal heart rhythms, and reducing oxidative stress. These mechanisms have yet to be confirmed in humans .

    Heart Failure

    Taking L-carnitine by mouth or intravenously (by IV) seems to improve symptoms and increase exercise capacity in people with heart failure. One study suggests that a combination of l-carnitine with ubiquinol, a form of CoQ10, may also improve symptoms of heart failure (the combination product is called Carni Q-Gel, by Tishcon Corporation) .

    In a 3-year-long study on patients with heart failure, L-carnitine appeared to increase survival rates compared to the placebo .

    Scientists are investigating the effects of a combination of taurine and L-carnitine on heart cells .

    Heart Inflammation (Myocarditis)

    Carnitine (D-L-carnitine) by mouth seems to reduce death rates from myocarditis associated with diphtheria, according to clinical trials .

    Overactive Thyroid (Hyperthyroidism)

    Some clinical evidence suggests that l-carnitine may improve symptoms of high thyroid hormones, such as rapid or pounding heartbeat, nervousness, and weakness .

    In one randomized trial, 2 and 4 grams per day of L-carnitine reversed hyperthyroid symptoms. In another study, L-carnitine relieved a “thyroid storm” .

    Some scientists believe that l-carnitine may inhibit both triiodothyronine (T3) and thyroxine (T4) entry into the cell nuclei. This is relevant because thyroid hormone action is mainly mediated by specific nuclear receptors .

    Infertility in Men

    Despite some mixed findings, most clinical studies suggest that L-carnitine increases sperm count and sperm motility in men with infertility .

    Some researchers have suggested that the amount of carnitine in semen is directly related to sperm count and mobility. Carnitine seems to provide more energy for sperm cells and it may reduce cell death in the testes, according to preliminary findings .

    A study of 100 infertile men revealed that the intake of carnitine supplements increased sperm motility .

    Infertile men with varicose veins in the scrotum (varicocele) took carnitine for 6 months (250 mg, 4x a day). Results showed increased sperm count, mobility, and concentration .

    Scientists are also exploring the antioxidant effects of carnitine on sperm in cells and in animals .


    Clomiphene is the typical treatment for infertility in women with PCOS. However, some women do not respond to this medication alone. Clinical research suggests that adding L-carnitine from day 3 of the cycle until the day of pregnancy testing to a clomiphene treatment cycles increases ovulation and pregnancy rates compared with placebo in these women .

    Valproic Acid Side Effects

    Valproic acid is an anticonvulsant drug that can reduce the body’s carnitine levels, potentially resulting in high ammonia levels, and brain or liver damage. L-carnitine supplementation in such individuals may prevent or reduce high ammonia levels (hyperammonemia) and the severity of liver and brain damage, according to some clinical trials .

    Insufficient Evidence for:

    The following purported benefits are only supported by limited, low-quality clinical studies.

    There is insufficient evidence to support the use of carnitine for any of the below-listed uses.

    Remember to speak with a doctor before taking carnitine supplements. Carnitine should never be used as a replacement for approved medical therapies.

    Weight Loss

    L-carnitine is often marketed as a weight loss aid and performance enhancer, but there is insufficient evidence to back up these purported benefits.

    The evidence so far has been mixed and inconsistent. According to one analysis of clinical trials, L-carnitine may reduce weight by about 1.3 kg and decrease body mass index by about 0.5 kg/m2 compared to control in both nonobese and obese adults .

    One trial suggests it may help reduce weight in overweight people with diabetes when used as an add on to the anti-obesity drug orlistat .

    In another study of overweight women diagnosed with polycystic ovary syndrome, carnitine supplements reduced their weight, body mass index, and waist and hip size (circumference) .

    However, L-carnitine does not seem to affect weight loss in overweight or obese people without diabetes or PCOS. The effects of carnitine on weight loss also appear to weaken with time. Larger trials on more diverse populations are needed .

    Body Composition and Performance Enhancement

    According to one unproven hypothesis, younger people have a sufficient amount of carnitine in the body, unlike older people. In line with this, carnitine has been researched for improving body composition and muscle mass in older people. The results have been mixed.

    The existing studies suggest that L-carnitine may be beneficial in weak patients over 75 years of age but that it likely isn’t beneficial in healthy older women .

    Others claim that carnitine may improve exercise endurance in all ages by increasing muscle carnitine levels, but data are lacking to support this claim .

    Some evidence suggests that maximal exercise in trained athletes is linked with lower L-carnitine blood levels .

    Initial studies have suggested that dietary carnitine stimulates the breakdown of fats into energy, reduces the amount of lactic acid produced during exercise, and speeds up recovery from exercise stress. Further studies failed to show any benefit of L-carnitine on athletic performance or endurance in male athletes or healthy men .

    Although it’s uncertain what caused these conflicting results, all these clinical trials suffered from flaws such as small sample sizes and short duration. Larger, longer, higher-quality trials are needed to determine the effects of L-carnitine on athletic performance.

    Fatigue From Disease and Aging

    Fatigue is common in cancer patients after treatments from chemotherapy, radiation therapy, and poor nutrition. Some scientists believe that low carnitine levels can contribute to this fatigue.

    Nonetheless, there is not enough evidence to rate the effectiveness of L-carnitine on fatigue from disease and aging.

    In a study of elderly subjects, acetyl-L-carnitine treatment reduced physical and mental fatigue, reduced muscle pain, and improved cognitive function .

    In one study, 250 milligrams of carnitine 3 times a day improved fatigue and quality of life in terminal cancer patients .

    One group of scientists are investigating the effects of acetyl-l-carnitine and lipoic acid on metabolic function in old rats. This combination has not been researched in humans .

    In Dialysis Patients

    Patients with kidney disease undergoing dialysis often have anemia with deformed red blood cells. The deformity prevents the blood cells from carrying enough oxygen to the body’s tissues, causing muscle weakness and fatigue .

    A study following dialysis patients found that carnitine supplements reduced red blood cell deformity and increased overall red blood cell count in 3 months .

    Another study on dialysis patients found that carnitine injections helped sustain higher levels of oxygen use (improved endurance), such as during exercise and also reduced overall fatigue .


    Evidence is lacking to determine the effects of carnitine on mood.

    Initial studies suggested that acetyl-L-carnitine has some antidepressant potential in elderly patients with age-associated depression .

    A study found that supplementing the diets of fibromyalgia patients with acetyl-L-carnitine improved depressive symptoms and reduced muscle pain .

    More human studies are needed.

    Scientists are also investigating the effects of acetyl-L-carnitine on mice with depression .


    It’s uncertain how L-carnitine affects cognition since clinical trials are limited.

    Some scientists proposed that carnitine levels gradually decline as Alzheimer’s progresses, suggesting that patients with Alzheimer’s could potentially benefit from acetyl-L-carnitine treatment .

    In one small study, acetyl-L-carnitine improved memory in older people and in Alzheimer patients. The authors suggested it might slow the progression of the disease, but proper trials would need to determine its mechanism and effectiveness .

    Theoretically, consuming carnitine helps the body produce acetylcholine. According to some hypotheses, this neurotransmitter declines as memory loss advances .

    Thus, carnitine might hypothetically increase energy production in brain cells that are starting to “slow down” and trigger memory loss. However, this is just a scientific hypothesis that has not been verified in clinical trials .

    Insulin Resistance

    Insulin resistance has been linked with obesity and increased levels of fat in lean tissue.

    Some researchers suggest that carnitine may improve insulin sensitivity by affecting fat oxidation in lean tissue and muscles. However, data are lacking to back up their theory .

    In a study of overweight women with polycystic ovary syndrome, carnitine supplements lowered glucose and insulin blood levels and reduced insulin resistance .

    Far more research is needed.

    Sleep Disorders

    One hypothesis says that sleep-disordered breathing is associated with heart damage and altered heart carnitine metabolism. Although carnitine levels are low in heart tissue in those with chronic heart failure, carnitine blood levels may be increased because of “leakage” from damaged heart cells and altered carnitine metabolism .

    Thus, some scientists think that carnitine supplementation can help patients suffering from obstructive sleep apnea, a condition where breathing repeatedly stops and starts during sleep. Carnitine helped improve airways for breathing and improved overall sleep quality in patients in one small study .

    In a study of elderly subjects, acetyl-L-carnitine treatment improved sleep quality .

    However, a study of fibromyalgia patients found no improvement in sleep disturbances by L-carnitine .

    Further clinical trials are needed to rate the effectiveness of L-carnitine for sleep disorders.

    Alertness in Narcolepsy

    Acylcarnitine levels are abnormally low in narcolepsy patients. L-carnitine supplements may improve daytime alertness in these patients. L-carnitine treatment increased acylcarnitine and reduced blood lipids. Large-scale trials are required .


    HIV patients may develop complications such as muscle, fat, and nerve degeneration. Carnitine supplements are being researched as a potential add-on strategy. In HIV positive individuals L-carnitine and acetyl-L-carnitine, as an add-on to conventional therapy, increased CD4 counts, reduced heart tissue damage, and reduced the number of triglycerides (fat) in the blood .

    According to one scientific theory, L-carnitine may block the enzyme acidic sphingomyelinase, which prevents sphingomyelin breakdown in cells .

    However, an initial study on patients with HIV-associated fat tissue degeneration did not find any evidence for using L-carnitine to reverse the effects of fat tissue degeneration. This study found that L-carnitine lowered cholesterol levels in the blood, but not the levels of triglycerides .

    Large-scale trials are needed before we can draw any solid conclusions.

    Lacking Evidence (Animal and Cellular Studies)

    No clinical evidence supports the use of carnitine for any of the conditions listed in this section.

    Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.

    Kidney Function

    In a rat model of chronic kidney disease, the administration of carnitine improved kidney function. Carnitine lowered the levels of creatinine and BUN in the blood, reduced kidney tissue damage and abnormal kidney enlargement .

    Bone Health

    In a mouse model of osteoporosis, L-carnitine and isovaleryl-L-carnitine stimulated bone formation, improving bone turnover, bone density, bone size, and bone structure .

    Another study found that dietary L-carnitine might improve the bone mineral content and bone mineral density in a female mouse model of postmenopausal bone loss. Results indicated slowed bone loss and improved bone structure .

    Some scientists hypothesize that carnitine might promote bone mineralization, in part by inhibiting thyroid hormone action .

    The effects of carnitine on bone health in humans are unknown.

    In mouse studies of drug-induced seizure, pre-treating the mice with L-carnitine suppressed seizures dose-dependently .

    A rat model of hyperthyroidism induced by L-thyroxine injections suggested that L-carnitine might have dose-dependent protective effects against liver damage .

    L-carnitine suppresses the onset of neuromuscular degeneration and increases the lifespan of mice with familial amyotrophic lateral sclerosis (ALS) .

    It’s unknown how carnitine affects seizures, liver health, and ALS in humans.

    L-Carnitine Side Effects & Precautions

    Side Effects

    In general, the adverse effects of oral or intravenous L-carnitine are mild and rare. It has been reported to cause vomiting, diarrhea, a fishy body odor, abdominal cramps, and nausea. More severe and rarer side effects are seizures and muscle weakness in people prone to heart disease .

    Pregnant women should avoid L-carnitine; insufficient data are available.

    Preclinical Safety Data

    These side effects have not been confirmed in humans.

    Some research suggests that carnitine is metabolized into TMAO, which changes cholesterol metabolism and may promote plaque build-up in the arteries. Theoretically, this leads to the degeneration of artery walls, restricted blood circulation, and blood clots. However, no human studies suggest that L-carnitine worsens cardiovascular health .

    Carnitine appears to block both triiodothyronine (T3) and thyroxine (T4) entry into the cell. Long-term use of L-carnitine accelerated the production of reactive oxygen species in the liver and blood in mice .

    L-carnitine may disturb kidney function by affecting ion transporters in mice .

    Acetyl-L-Carnitine (ALCAR) is the acetylated form of the amino acid L-carnitine (LC), which means ALCAR is L-carnitine tagged with an acetyl molecule.

    Whilst both forms can be used as a supplement, ALCAR is often preferred due to its ability to cross the blood-brain barrier allowing it to interact with nerves in the brain, and also donate its acetyl molecule, a key step in neurotransmitter formation, required for healthy brain activity.

    ALCAR and LC are naturally produced in the body and occur naturally in the diet, usually when we eat animal protein. However, ALCAR is commonly taken as a nutritional supplement due to numerous potential health benefits.

    A major function of ALCAR is to transport fatty acids across the membrane of the mitochondria (the powerhouse of the cell) in order to generate ATP (the energy currency of the body).

    During this process it is converted into LC as it donates its acetyl group.

    Where Acetyl-L-Carnitine comes from

    ALCAR can be produced or sourced in several ways. A major source are the liver and kidneys which produce ALCAR from the amino acids lysine and methionine, although the majority of LC is actually stored in skeletal muscle tissue.

    In the body, ALCAR is converted into L-carnitine once it has donated its acetyl group to help with fatty acid transport into the mitochondria. However, it is possible to revert this reaction and convert L-carnitine back into ALCAR, and this frequently occurs in the cell as part of normal metabolism. The final natural source of ALCAR is the diet, with red meats, especially leaner muscle rich cuts being, a particularly high source. Other foods such as white meats, cheeses and some fruits and vegetables like avocados and asparagus also contain L-carnitine, although to a much lesser degree.

    Supplementation with Acetyl-L-Carnitine

    Whilst ALCAR deficiency is very rare, ALCAR supplementation is very common and popular due to numerous potential health benefits. ALCAR is preferred to LC as a supplement due to its increased bio-availability,1 meaning it is more readily absorbed from the gut, and its ability to cross the blood-brain barrier allowing it to modulate numerous functions in the brain.2

    Benefits and of Acetyl-L-Carnitine

    Numerous health benefits have been described for ALCAR and LC, below we cover the potential major benefits and inform you of the latest research.

    Enhanced cognition and neuroprotection

    A major function of ALCAR and LC in the brain is in the formation of neurotransmitters, required for proper function of the brain. Several promising studies in animal models demonstrated a marked improvement in cognition.3 A similar improvement was seen in elderly populations4 and those suffering from Alzheimer’s Disease.5 Of particular interest was the ability of ALCAR to slow the progression of Alzheimer’s Disease in early onset patients.

    Together these findings suggest that ALCAR is a potent neuroprotectant, facilitated by its ability to cross the blood brain barrier. It is not yet clear how ALCAR exerts its protective effect in the brain, but potential hypotheses include improved neurotransmitter synthesis, or improved energy generation in neurons preventing their damage.

    What is also unknown is the effect on cognition, and any neuroprotective benefit, in younger or healthy individuals remains unknown, some positive results have been reported,6 however a large scale confirmatory study is still required.7

    Mood Boosting

    Due to its important role in the brain as a supplement for neurotransmitter formation another logical investigation was the role of ALCAR and LC on mood.

    In both animal8 and human studies9 a significant improvement in mood was observed following ALCAR supplementation.

    A review of numerous studies recommended that a large scale clinical trial be performed to identify exactly who may be of benefit. However, they suggest that ALCAR may be an important antidepressant therapy, either alone or in conjunction with other mood enhancers, especially in those with other medical conditions who may not tolerate high dose antidepressants.10

    Improved sleep quality

    Rather than a general improvement of sleep quality, ALCAR has been shown to have several highly specific benefits. In those suffering from narcolepsy, a rare disorder where the brain cannot regulate the normal sleep cycle, LC treatment promoted daytime wakefulness.11 A beneficial effect in those who suffer from sleep apnea was also observed.1213 Again, its benefit in healthy individuals remain unknown.

    Fat busting and muscle promotion

    Due to its role in energy generation, specifically involving fat metabolism, and its abundance in muscle tissue there was much excitement about using ALCAR as a fat buster or muscle builder. However, several studies in both animal models14 and humans,15 have shown no benefit on either activity, or even on muscle LC content in normal individuals. Some studies have reported a benefit in elite endurance athletes with a high energy intake and expenditure. In these athletes, LC is thought to promote the usage of fat in energy generation, preserving some of the muscles natural energy source, therefore delaying the point when they “hit the wall.”1617

    Interestingly in a rat model, ALCAR and alpha-lipoic acid co-supplementation was able to improve metabolic function, burning energy more efficiently, whilst also reducing oxidative stress.18 No similar improvement was observed in a human trial looking at depression.19 Again their role in healthy individuals remains un-investigated.

    Genes and SNPs

    At the genetic level ALCAR has been shown to be of significant direct benefit to those carrying the risk ‘C’ allele of rs5770917, located between the CPT1B and CHKB genes, which is associated with narcolepsy.2021 In these individuals a daily dose of 510 mg ALCAR was effective at reducing daytime sleepiness.

    Due to ALCAR’s important role in energy generation it may be of interest to those who carry risk SNPs in the IL-4, IL-6, IL-1β, IL-10, TNFα, TRPM3 and TRPA1 genes, although to date no studies have been performed to investigate this effect.222324

    Our mitochondria within our cells contain their own DNA, and this DNA DNA is also subject to variation in the form of SNPs like our main genome. Two SNPs within the mitochondrial genome have been identified which associate with fatigue, but again no studies investigating ALCAR as a potential therapeutic have been performed.25

    Dosing ALCAR

    ALCAR is approved by the FDA for the treatment of certain LC deficiency syndromes. It is also available as an over the counter nutritional supplement. No official dosing advice has been provided however doses of 500 – 2000 mg per day are typically used.26

    Any described side effects?

    At doses of approximately 3,000 mg per day, carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a “fishy” body odor. Rarer side effects include muscle weakness in uremic patients and seizures in those with seizure disorders.27

    Furthermore, some research indicates that intestinal bacteria can break down carnitine to form a substance called TMAO that might increase the risk of cardiovascular disease, particularly in those who eat a meat rich diet.28 Interestingly a study published by the Mayo Clinic29 reported seemingly opposite findings, showing a protective cardiac effect.

    Carnitine and TMAO

    Whilst these may seem counterintuitive the negative reference refers to the formation of TMAO from intestinal bacteria rather than from cells within the body. It is possible therefore that a poor gut biome, or indeed even the source of ALCAR/LC may be important in describing outcomes. A diet rich in red meat has been shown to disrupt the gut biome and so other ALCAR/LC sources may be preferred.3031

    L-carnitine is another supplement that sounds crazy confusing, so we’re here to break apart the fact from the fiction. So, what exactly is this interesting supplement?

    It’s been used by athletes all around the world for its fat-burning capabilities, since it could potentially optimise how your body uses fat as a fuel source, leading to greater exercise performance.3 L-carnitine is a popular supplement for weight loss and fat burning purposes, and when taken correctly, could be a great addition to your training regime. Let’s find out more…

    What is L-carnitine?

    It’s a non-essential amino-acid-like compound, meaning it’s produced in the body naturally.

    You can get a certain amount of L-carnitine from your diet, as it’s found in foods such as red meat — typically the redder the meat, the better. Plant sources such as avocado and soybean contain small amounts too. Supplements should be consumed alongside a healthy diet, but are often recommended to anyone who struggles to get enough of a certain nutrient in their diet.5

    L-carnitine is responsible for transporting long-chain fatty acids to your cells’ mitochondria, where energy is then produced as the fat is oxidised and used for fuel. More than 95% of the body’s L-carnitine stores are found in skeletal muscle (muscle which is connected to your skeleton), along with trace amounts in the liver and blood.6

    Benefits of L-carnitine

    1. Weight Loss

    It’s been theorised that L-carnitine could help your body to produce energy by utilising the body’s fat stores, allowing you to work out for longer and ultimately aiding in fat loss. Evidence suggests it may promote weight loss by increasing calorie expenditure.6 Taking it daily has been proven to increase the blood and muscular concentrations of this amino acid-like compound, which could enhance fat metabolism as a result with increased muscle carnitine concentrations.6

    2. Exercise Performance & Recovery

    Given its potential fat-burning capabilities, it’s thought that L-carnitine optimises how your body uses fat for fuel, allowing you to exercise for longer.7 Some research has also found that 3 weeks’ supplementation with an L-carnitine supplement reduces muscle damage from high intensity exercise bouts.7

    Supplementing with L-carnitine could also play an important role in recovery from strenuous exercise, with suggested doses of 2-4g daily to optimise results.6 There’s initial evidence that this could lead to a reduction in various markers of metabolic stress and muscle soreness which is replicated in many studies. However, research is still limited and further studies are needed to enhance the scientific evidence for l-carnitine supplementation.2

    How Does L-Carnitine Work?

    When you exercise, thousands of biochemical reactions are taking place inside your body. One of these is the action of your enzymes starting to break down stored fat into fatty acids and glycerol, a sugar alcohol. These are then used as fuel throughout exercise.

    Studies have theorised that L-carnitine is a compound that plays an important role in this process of fat metabolism as its key role is to transport the long-chain fatty acids across the inner membrane. These fatty acids are thought to be the main energy sources used during low- to moderate intensity exercise.2

    Types of L-carnitine and Their Uses

    The two main variations of L-carnitine that are supplemented in the diet are L-carnitine tartrate and acetyl L-carnitine.

    1. L-carnitine Tartrate

    L-carnitine Tartrate is one of the most common forms of L-carnitine found in sports nutrition supplements due to its rapid absorption rate.9 It’s created in the body from the amino acids lysine and methionine and is mainly synthesised in the liver and kidneys before being transported for use in other tissues in the body.

    L-Carnitine Tartrate is found in its highest levels in tissues that use fatty acids as the main fuel source, such as the skeletal and cardiac muscles. It should be taken in conjunction with a healthy, balanced diet and exercise regime.3

    2. Acetyl L-carnitine (ALCAR)

    Acetyl L-carnitine is created in the body from the amino acids lysine and methionine. ALCAR has an acetyl group attached to the carnitine molecule. This allows it to pass through the blood-brain barrier making it the most bio-available, and thus most easily absorbed, form.

    ALCAR is ideal for athletes and active people who take part in regular exercise or anyone looking for an easy-to-consume source of L-carnitine that can be taken throughout the day.3

    When to take L-carnitine

    Studies have observed that l-carnitine, when taken with 80g carbohydrates, has positive effects, as a 20% increase in muscle carnitine content was seen with 12 weeks of supplementation.8

    The combination of l-carnitine and carbohydrates prevented an 18% increase in body fat mass accumulation associated with taking only carbohydrate supplementation in healthy young males.6

    Taking this supplement with a decent amount of fast-acting carbohydrates may be of greater benefit as insulin, a hormone which is released when you consume carbohydrates, stimulates carnitine transportation into skeletal muscle (i.e. 60g of dextrose or maltodextrin).8

    Whilst there’s some evidence to suggest that L-carnitine can take effect approximately 30-45 minutes after consumption, the “before or after workout” dilemma ultimately doesn’t seem to be the most important factor when considering supplementing with it.6 Rather, take it daily for a few weeks to increase carnitine stores and you should be able to see some impactful results.6

    Dosage – How much do you take?

    Studies suggest varying doses for each form of L-carnitine for best results, the following is deemed optimal for each form of carnitine:5

    Take Home Message

    It has been suggested that L-carnitine has the ability to move more fatty acids into your cells to be burnt for energy, making it an effective performance enhancer, and it may also be beneficial for fat burning and weight loss.

    While there are some positive results with l-carnitine supplementation, it must be considered that overall scientific evidence is lacking.

    The various forms of L-carnitine are perfect supplements for people who don’t easily acquire it from natural food sources as a part of their normal diet.

    Let’s face it: Amino acids are crucial to pretty much every aspect of health. These compounds are the building blocks of proteins, which make up our skin, hair and muscles and perform a variety of functions in the body. When it comes to health, though, some amino acids, like L-carnitine and glycine, stand out from the rest.

    Found only in small amounts in certain foods like beef, fish and chicken, it’s safe to say that many of us aren’t getting enough L-carnitine in our diets. Fortunately, it’s also available in capsule, liquid or injection form to help supply a quick and concentrated dose of carnitine.

    This superstar supplement has been shown to do everything from enhance athletic performance to bring fat burning to the next level. Here’s what you need to know about this important amino acid and what it can do for you.

    What Is L-Carnitine?

    Carnitine is a type of amino acid that benefits energy levels by transporting fatty acids into the mitochondria where they can be burned up and used as fuel. For this reason, many take carnitine as a weight loss supplement to help bump up fat burning.

    Carnitine occurs in two forms, or isomers: L-carnitine and D-carnitine.

    L-carnitine is the active form that plays a role in energy metabolism and production. It is produced within the body, but it can also be taken as a supplement or found in many different protein foods as well.

    In supplement form, it’s available as a capsule, liquid or even injectable.

    A deficiency in carnitine can be caused by an inadequate intake, excess loss through diarrhea or dialysis, liver disorders, the use of certain medications, and some genetic disorders.

    Additionally, because it is primarily found in animal products, vegans and vegetarians are at a higher risk of deficiency.

    Although many people take L-carnitine as a way to speed up weight loss and fat-burning, carnitine benefits include enhancing brain function, preventing muscle damage, regulating blood sugar and increasing endurance as well.

    Different Types

    There are several different forms of carnitine available. Here are a few of the most common types:

    • Acetyl-L-carnitine: This type of carnitine is thought to benefit brain health and memory and has been processed so that it’s able to easily pass the blood-brain barrier.
    • D-carnitine: Also known as the inactive form of carnitine, supplementing with this form can actually cause a carnitine deficiency by blocking the absorption of other active forms.
    • L-carnitine L-tartrate: This type is often found in sports supplements, thanks to its ability to reduce muscle soreness and boost physical performance.
    • Propionyl-L-carnitine: This form helps increase levels of nitric oxide in the body, which dilates the blood vessels to promote better blood flow.
    • L-carnitine fumarate: Preliminary research suggests that this type of carnitine could help support bone health to protect against age-related bone loss.


    1. Increases Endurance

    Because L-carnitine plays a central role in energy production, many use it for bodybuilding and athletic performance as a way to enhance endurance and boost energy levels.

    In one study out of Turkey published in the Journal of Strength and Conditioning Research, giving professional soccer players three to four grams of L-carnitine before exercise was found to prolong the time it took to reach exhaustion.

    Similarly, an animal study out of India published in the journal Wilderness & Environmental Medicine showed that giving rats L-carnitine improved exercise endurance.

    For this reason, supplementing with this amino acid may especially benefit endurance athletes, such as long-distance runners, swimmers or cyclists.

    2. Enhances Weight Loss

    Many people look to L-carnitine as a way to help shed unwanted pounds and lose weight fast. When combined with diet and exercise, some studies have found that supplementing with it can, in fact, be an effective way to enhance weight loss.

    One analysis of research out of Iran looked at the results of nine studies and found that supplementing with carnitine led to a significantly greater amount of weight loss as well as a larger drop in body mass index compared to a control group.

    However, L-carnitine weight loss results may vary, and other studies have turned up mixed results.

    In a study out of Australia published in the International Journal of Sports Nutrition and Exercise Metabolism, for instance, 36 obese women took either L-carnitine or a placebo and completed eight weeks of aerobic training. At the end of the study, researchers concluded that L-carnitine had no impact on either total body mass or fat mass.

    While L-carnitine may work for some people, it shouldn’t be considered a quick fix. Pair it with regular exercise and a healthy diet to see maximum results.

    3. Prevents Muscle Damage

    Besides increasing endurance and amping up weight loss, this amino acid also makes a useful supplement for athletes looking to prevent and protect against muscle damage.

    In one 2014 study published in the Asian Journal of Sports Medicine, 21 male athletes were given either L-carnitine or a placebo daily for two weeks prior to an athletic test. Compared to the control group, those who took L-carnitine were found to have lower levels of certain markers that indicate muscle damage.

    4. Amps Up Fat-Burning

    Besides increasing weight loss, this amino acid also helps kick up fat-burning as well.

    In one study conducted in Germany, overweight participants received a regular diet, either with or without the addition of L-carnitine. After 10 days, L-carnitine was found to significantly increase the breakdown of fat.

    Another study published in the Journal of Physiology showed that increasing the amount of carnitine in the muscles helped prevent fat gain by increasing fat burning and energy expenditure during physical activity.

    5. Boosts Brain Function

    L-carnitine isn’t just good for your body, but it’s good for your mind as well. In fact, promising research has found that it may positively impact brain function and cognition.

    One study conducted by the University of Catania in Italy and published in the American Journal of Clinical Nutrition looked at the effects of daily L-carnitine supplementation on mental and physical fatigue in elderly participants over 100 years old. Not only was it found to reduce total fat mass and increase muscle mass, but it also helped decrease fatigue and improve cognitive function.

    Other studies have even found that acetyl-L-carnitine, another form of L-carnitine, could help reverse cognitive decline and improve memory in patients with Alzheimer‘s disease.

    6. Regulates Blood Sugar

    Some promising research has shown that carnitine supplementation could aid in maintaining normal blood sugar levels and fighting insulin resistance.

    Insulin is the hormone responsible for transporting sugar from the bloodstream to the cells where it can be used as fuel. Too much insulin can lead to insulin resistance, decreasing its effectiveness and resulting in high blood sugar.

    A study out of Rome published in the Journal of the American College of Nutrition showed that infusing people with diabetes with L-carnitine improved insulin sensitivity and increased the uptake of sugar from the bloodstream.

    Another small study in 2010 conducted at Sapienza University’s Department of Clinical Medicine in Rome found that combining L-carnitine with caloric restriction helped reduce insulin resistance and increase sensitivity.

    Food Sources

    Animal products are the best natural sources of L-carnitine, with foods like grass-fed beef packing in the highest amount per serving. It can also be found in small amounts in some sources like vegetables and grains.

    Here are the foods that contain the most L-carnitine per serving, according to the National Institutes of Health:

    • Beef steak, cooked, 4 ounces: 56–162 milligrams
    • Ground beef, cooked, 4 ounces: 87–99 milligrams
    • Whole milk, 1 cup: 8 milligrams
    • Codfish, cooked, 4 ounces: 4–7 milligrams
    • Chicken breast, cooked, 4 ounces: 3–5 milligrams
    • Ice cream, 1/2 cup: 3 milligrams
    • Cheddar cheese, 2 ounces: 2 milligrams
    • Whole wheat bread, 2 slices: 0.2 milligram
    • Asparagus, cooked, 1/2 cup: 0.1 milligram

    Supplements and Dosage

    Although carnitine can be found naturally in plenty of food sources, it’s also available in supplement form as well.

    The first step is deciding what form to use and when to take your supplement. It can be found in L-carnitine liquid, capsule and injectable forms for a quick and convenient way to boost your carnitine levels.

    For oral L-carnitine, be sure to take it with meals to maximize its effectiveness.

    The standard L-carnitine dosage is 500–2,000 milligrams daily. Based on most current research available, a dose of up to two grams per day can be used safely and effectively with minimal side effects.

    The dosage may vary by the type of L-carnitine supplement, however. Acetyl-L-carnitine, for example, can be used in doses up to 2,500 milligrams per day while the dose for L-carnitine L-tartrate, a form typically used to enhance athletic performance, can range all the way up to 4,000 milligrams.

    Keep in mind that when adding any supplement into your routine, you should always start with a low dose and work your way up to ensure you’re able to tolerate it without adverse side effects.

    Related: L-Glutamine Benefits Leaky Gut & Metabolism

    Uses and Recipes

    Most people use L-carnitine to help boost weight loss and increase fat burning. However, there are many other potential reasons you may want to add carnitine into your diet.

    It can correct deficiencies, boost brain function, prevent muscle damage, increase endurance and enhance athletic performance.

    It can also be incredibly useful for vegans and vegetarians who may have a limited intake of carnitine-rich foods. Taking a supplement can be an easy way to help meet your needs for this crucial amino acid.

    If you’re looking for some ways to increase your carnitine intake without the use of a supplement, including a few servings of carnitine-rich foods can help. Here are some recipes that are high in carnitine for you to try out:

    • Steak Fajitas
    • Garlic Baked Chicken
    • Seared Grass-Fed Steak
    • Savory Baked Fish

    Risks and Side Effects

    When used as directed, carnitine can be safe and effective with minimal risk of side effects. Common L-carnitine side effects include stomach pain, nausea, vomiting and diarrhea.

    L-carnitine may increase the risk of seizures in those with epilepsy. If you’ve had a seizure before, you should not take carnitine.

    Additionally, carnitine may worsen symptoms of hypothyroidism. If you have an underactive thyroid, you should consult with your doctor before taking this amino acid.

    When starting carnitine, as with any supplement, it’s best to start with a low dose and increase slowly to assess tolerance. If you experience any negative side effects, be sure to report to your doctor to determine if supplementation is right for you.

    Finally, keep in mind that carnitine may enhance fat loss and weight loss for some people, but it should be used in combination with a healthy diet and active lifestyle to see the most results.

    Final Thoughts

    • What is L-carnitine? Carnitine is an amino acid that works by transporting fatty acids to the mitochondria where they can be broken down into fuel.
    • This amino acid is produced in the body and is also found in small amounts in certain types of food, like animal products.
    • Although safe in moderation, potential carnitine side effects include stomach pain, nausea, vomiting and diarrhea.
    • When paired with a healthy lifestyle and nutritious diet, taking carnitine could offer a variety of health benefits.
    • In fact, studies show that L-carnitine benefits endurance, enhances weight loss, prevents muscle damage, amps up fat-burning, boosts brain function and regulates blood sugar.

    Carnitine (L-carnitine)

    Peyronie Disease

    Peyronie disease is characterized by a curvature of the penis that leads to pain during an erection. One promising study compared acetyl-L-carnitine to the medication tamoxifen in 48 men with this condition. Acetyl-L-carnitine worked better than tamoxifen at reducing pain during sex and reducing the curve of the penis. Acetyl-L-carnitine also had fewer side effects than tamoxifen. More research is needed.


    Some research suggests that L-carnitine may help prevent or reduce symptoms of an overactive thyroid, such as insomnia, nervousness, heart palpitations, and tremors. In fact, in one study, a small group of people with hyperthyroidism saw these symptoms improve, and their body temperature become normal, when taking carnitine. But a larger, better-designed clinical trial is needed to see if carnitine really works. In addition, researchers think carnitine may work by blocking the action of thyroid hormone, which could be dangerous for people with low thyroid levels. DO NOT take carnitine for hyperthyroidism without your doctor’s supervision.

About the author

Leave a Reply

Your email address will not be published. Required fields are marked *