Vitamin b12 side effect


Vitamin B12

Vitamin B12 is the common name for a nutrient known scientifically as methylcobalamin.

It’s used as a dietary supplement and to treat certain anemias.

Vitamin B12 plays an important role in helping the body make red blood cells.

If you have low levels of vitamin B12, you may feel weak, have less energy, and experience slow thinking — a condition called pernicious anemia.

Other symptoms of pernicious anemia include numbness or tingling in the fingers and toes.

Your doctor will run blood tests to determine if your B12 levels are low.

People who eat a plant-based diet (vegans) are at greater risk because animal products often contain vitamin B12 naturally.

Older people are at higher risk of a vitamin B12 deficiency, too, because your body has a harder time absorbing the vitamin as you age.

Also, low levels of folic acid and low levels of vitamin B12 tend to go hand-in-hand.

Vitamin B12 Foods

Vitamin B12 can be found naturally in foods such as clams, mollusks, and liver.

Fish such as tuna, rainbow, wild, or cooked trout, sockeye salmon, and haddock are also good sources of B12.

And meats like lamb, veal, and beef, and dairy products such as yogurt, milk, and cheese contain high levels of vitamin B12.

The Different Types of Vitamin B12

While some forms of vitamin B12 exist naturally, others are made in laboratories.

The most-commonly used man-made forms are cyancobalamin, methylcobalamin, and hydroxocobalamin.

You can buy cyanocobalamin tablets over-the-counter (OTC) in low doses, but you’ll need a prescription to get higher doses, which are available in liquid or spray.

Methylcobalamin is the form of vitamin B12 that’s the easiest for the body to use.

You don’t need a prescription to buy methylcobalamin, but it can be harder to find and more expensive than the other forms.

Hydroxycobalamin is the form of vitamin B12 that the “good” or “healthy” bacteria in your gut make on their own. It’s available by prescription and only as an injection.

In addition to helping boost vitamin B12 levels, hydroxycobalamin is also used to treat cyanide poisoning.

Vitamin B12 Warnings

Talk to your doctor before taking vitamin B12 if you:

  • Are allergic to vitamin B12 or any other ingredients found in the drug
  • Have a genetic condition called optic atrophy where the nerve that connects the eye to the brain wastes away
  • Have blood in your urine
  • Have an ongoing infection
  • Have low iron or folate levels
  • Have a bone disease called polycythemia

Pregnancy and Vitamin B12

Depending on its form and the dose, vitamin B12 has two different safety profiles for pregnant women.

Vitamin B12 tablets that you swallow or let melt under your tongue are considered safe during pregnancy.

It’s not clear, however, whether high-dose vitamin B12 could harm your unborn baby.

In either case, you should tell your doctor if you are pregnant or plan to become pregnant before taking this medication.

You should also tell your doctor if you are breastfeeding or plan to breastfeed.

Vitamin B12 is found in breast milk and is therefore not recommended for mothers who are breastfeeding.

Vitamin B12 Benefits


  • What does vitamin B12 do?
  • The 5 functions of vitamin B12
  • Vitamin B12 health benefits

Vitamin B12 Benefits: The Body Needs Vitamin B12

Vitamin B12 is an essential vitamin; the body cannot create it alone and therefore without a regular supply of B12 it is not possible to maintain good health in the long term. Biologically-speaking, vitamin B12 is vital – yet what are the main effects that it has on the body?

The 5 Functions of Vitamin B12

The workings of B12 can be divided into 5 key areas:

  1. Synthesis of DNA – the vitamin influences cell division and blood formation
  2. Energy metabolism – B12 is vital for energy production in the mitochondria
  3. Lipid metabolism – vitamin B12 is important for the building and maintenance of the cell membrane and myelin sheaths, a protector of the nerves in the central nervous system and brain
  4. Synthesis of hormones and neurotransmitters – the vitamin is needed to produce crucial neurotransmitters and therefore influences mood, psyche and perceptions
  5. Detoxification – homocysteine and cyanide are neutralised by B12, as well as radicals such as nitric oxide and peroxynitrite. The vitamin is an important opponent to nitrosative stress

Vitamin B12 is a fundamental, biological building block, essential to these important metabolic processes. Without the vitamin these vital functions cannot be maintained, having detrimental repercussions on the body.

Vitamin B12 Deficiency

Because vitamin B12 is involved in several fundamental metabolic processes, it plays a central role in maintaining general health. Therefore, vitamin B12 deficiency can have serious consequences.

Area Consequences of Vitamin B12 Deficiency
1. DNA synthesis Anemia, damaged mucous membranes, risk of cancer
2. Energy metabolism Chronic fatigue, sluggishness, poor performance
3. Lipid metabolism Damage from nerve tingling, numbness, chronic pain, paralysis, dementia
4. Hormones & Neurotransmitters Depression, psychoses, schizophrenia
5. Detoxification Chronic diseases, immunodeficiency

These are just a few examples of the immense and diverse effects of B12 on health. In fact, there are a myriad of vitamin B12 deficiency symptoms; in many respects we are just beginning to fully comprehend the importance of this vitamin.

For more information on diagnosing deficiency, see our article: Vitamin B12 Deficiency Tests.

How Does Vitamin B12 Work in the Body?

How might we begin to explain the various biological workings of vitamin B12? The simplest way is to focus on the three vitamin B12 forms and pathways through which the vitamin functions:

  1. Methylcobalamin works in the cell plasma
  2. Adenosylcobalamin functions in the mitochondria
  3. Hydroxocobalamin takes effect in the blood and cell plasma

Methylcobalamin and adenosylcobalamin are known as the “bioactive coenzymes” of vitamin B12: only in these chemical forms can the vitamin be directly utilised in the body. Hydroxocobalamin, on the other hand, does not function as a coenzyme, but scavenges toxins/free radicals.

In the cell plasma, as methylcobalamin, vitamin B12 is involved in the activation of folic acid and the conversion of damaging homocysteine into the important amino acid, methionine. Methionine, in turn, is the source of S-adenosylmethionine (SAM), a central methyl group donor needed to synthesise many hormones and neurotransmitters. Without vitamin B12, another vitamin – folic acid – cannot become active, which can indirectly trigger many other problems.

As adenosylcobalamin B12 works in the mitochondria; the power plants of the body. There, adenosylcobalamin is active in the citrate cycle, an important metabolic process for the generation of energy. B12 helps to break down harmful methylmalonic acid into succinyl-coenzyme A, an important building block in the reaction chain of the citric acid cycle. In order to take effect, adenosylcobalamin depends on a sufficient supply of biotin.

Above all, these two processes explain the tremendous impact of vitamin B12.

Hydroxocobalamin does not work as a coenzyme, but passively in the blood and cell plasma, where it binds to toxic substances, like cyanide and nitric oxide, and transports them out of the body.

Supplementing Vitamin B12

All three natural forms of vitamin B12 have important, independent functions in different biological cycles. The body therefore needs all three forms in equal measure – and fortunately they are interconvertible.

When it comes to vitamin B12 supplements, many experts believe that the coenzyme forms of B12 are the ideal agents to obtain (18). In contrast, the long-term use of artificial cyanocobalamin supplements does not have a direct biological effect and must first be converted in the body into one of the three natural forms of B12. It is therefore used less and less today and has sometimes been heavily criticised (19).

In natural B12 food sources there is always a mix of the three organic forms of B12 – a condition that is recreated in some B12 supplements today. In our opinion, supplements that contains a mix of all three natural B12 ingredients are optimal for achieving health benefits.

Finding Suitable Supplements Online

Dose/Day Active Ingredients Online Search
500 µg Methyl-, adenosyl- and hydroxocobalamin B12 + methylcobalamin + adenosylcobalamin + hydroxocobalamin + 500µg + bioactive
1000 µg Methyl-, adenosyl- and hydroxocobalamin

B12 + methylcobalamin + adenosylcobalamin + hydroxocobalamin + 1000µg + bioactive

For further details on supplement dosages, .

The 5 Functions of Vitamin B12 in Detail

In the following, we will take a detailed look into the five main biological areas in which vitamin B12 takes effect. There are also certain link available, which lead to an even more detailed explanation of these areas.

1. Vitamin B12 and DNA Synthesis

The most well known working of vitamin B12 is its influence on blood formation, as a severe deficiency of the vitamin leads to anemia. At the same time – and less obviously – many other areas are affected, in which cell division plays a major role, including in the brain and spinal cord. B12 deficiency causes transcription errors during DNA synthesis, which is likely to increase the long term risk of cancer and is linked to many chronic diseases (17).

2. Vitamin B12 and the Energy Metabolism

Equally well known is the fact that vitamin B12 has a significant impact on energy levels and physical performance. This is because the vitamin is directly involved in cellular energy production. Energy is transmitted in the body through a molecule called ATP (adenosine triphosphate) – a universal energy source that stores the energy gained from food and makes it available for physical processes. Fats, proteins and sugars are first broken down by the body and the intermediate products are then converted into water, CO2 and ATP in what is known as the citric acid cycle. In this cycle, vitamin B12 plays a crucial role – without it, the body does not manage to generate much-needed energy from food.

3.Vitamin B12 and the Lipid Metabolism

Vitamin B12 is also involved in the metabolism of membrane-forming lipids: the building blocks of the cell membrane and the myelin nerve protection layer. Unfortunately, the exact interconnections are not yet fully understood. In the future it may emerge that B12 is somewhat vital in this area, as the cell membrane is, in a sense, the communication surface of the cell. The consequences of B12 deficiency on the lipid metabolism however remains under-researched – better understood are the effects on the nerves.

Vitamin B12 and Nerves

Perhaps the most important long-term effect of vitamin B12 is its function in the central nervous system, including the spinal cord and brain. Here, the vitamin is involved in the formation of the myelin sheaths: a protective covering around the nerves, which can roughly be compared with the isolation of electrical cables. In the case of diseases such as multiple sclerosis (MS), this protective layer is destroyed, which means that the nerves can no longer transmit their signals correctly. Such conditions are also referred to as demyelinating diseases and are suspected to be closely related to B12 deficiency. Above all, a connection between B12 and MS is suspected, but so far insufficiently researched (2, 3).

More information: Vitamin B12 and Nerves

Vitamin B12 has a Regenerative Effect on Nerves

All in all, vitamin B12 is said to play a major role in the regeneration of nerves and can thus be applied as a potential therapeutic agent for a wide range of diseases. In studies on rats, it has now been shown that very high doses of methylcobalamin are capable of greatly enhancing the regeneration of nerves, which could be of great help in the treatment of a number of diseases (6). However, human studies have not yet been conducted.

Further reading: Vitamin B12 as Medicine

Vitamin B12 for Multiple Sclerosis, Fibromyalgia and Chronic Fatigue Syndrome

Vitamin B12 has been experimentally studied and successfully used in the treatment of MS, fibromyalgia, and chronic fatigue syndrome (CFS). Which workings of B12 play a role here is not yet fully clear. While in MS the myelin-forming property of the vitamin has been suggested as a key factor; in fibromyalgia and CFS it has been proposed that the properties of B12 as a homocysteine depressant (7) or nitric oxide scavenger are responsible for positive results (8).

Vitamin B12 and the Brain

The vitamin also plays an central part in the development of the brain. Some rare hereditary diseases prevent the synthesis of the B12 coenzymes, methylcobalamin and adenosylcobalamin. From studying these diseases, we now know that the vitamin is central to cerebral development and function (9). Without it, the brain develops poorly, potentially leading to a number of disorders and underdeveloped cognitive abilities.

Studies on children with strict vegan and vegetarian diets and B12 deficiency showed significant underdevelopment in the brain, a lower brain mass and a disadvantaged mental development. However, such negative consequences can usually be combatted through B12 supplements (10-16). Once again, it is the myelination of the nerves that is responsible for much of the brain damage caused by B12 deficiency. But also different methylation processes, due to a B12-related deficiency of S-adenosylmethionine, seem to be causally involved in neuropsychiatric problems.

4. Hormones and Neurotransmitters

Another under-researched area – that nonetheless shows great potential – is the connection between B12, hormones and neurotransmitters. Here, the vitamin is important for: maintaining mental abilities, perceptions and thought capacity; the function of the brain; and the regulation of physical processes through various neurotransmitters. The spectrum of action here ranges from the treatment of severe mental illness, which can be partially or even completely cured through B12 therapy, to the treatment of minor sleep disorders.

Vitamin B12 and Mental Illness

The association between B12 and various neuropsychiatric diseases is becoming increasingly clear (4). Even in the absence of extremely low levels of B12, these diseases can occur with pronounced B12 deficiency anemia. Sometimes even a slight vitamin B12 deficiency can lead to such diseases. In certain cases it has been reported that the most severe symptoms can be completely rectified through the administration of the vitamin (5). This is partly explained by the demyelisation of the nerve cords in the spine. In other mental illnesses such as depression, B12 plays a role because it has an effect on the formation of neurotransmitters – special chemical messengers that significantly affect our mood.

More information on this topic can be found in the article: Vitamin B12, Brain and Psyche

5. Vitamin B12 for Detoxification

B12 has further effects that are not directly related to its central functions in the body. Hydroxo- and methylcobalamin can be used to detoxify the dangerous substance cyanide (also hydrocyanic acid); the vitamin binds to cyanide so that it can be excreted through the urine. B12 is used, for example, in the treatment of burn victims who are suffering from smoke poisoning. Small amounts of cyanide, which we take in through the environment, can be detoxified by B12. This is especially relevant for smokers who constantly inhale cyanide through cigarettes. Yet even more effective is its role as an opponent of free radicals and its effect in combatting nitrosative stress – an underestimated and possibly central element in the development of many diseases.

Nitrosative Stress: B12 as a Nitric Oxide (NO) Scavenger

Excess nitric oxide (chemical formula: NO) also binds to vitamin B12, preventing nitrosative/oxidative free radical stress. Nitrosative stress is associated with a variety of diseases, such as: autoimmune diseases, eczema, psoriasis, asthma, heart attacks, strokes, dementia, Alzheimer’s, Parkinson’s and cancer – although the exact connections here remain under-researched.

In contrast, the negative effects of deficiency on the mitochondrial function, cholesterol metabolism, synthesis of steroid hormones (sex hormones) and formation of carcinogenic nitrosamines are relatively well comprehended. Vitamin B12 binds to nitric oxide to form nitrosocobalamin, which can easily be excreted through the urine. In orthomolecular medicine, quite dramatic healing effects have been reported as a result of B12 treatments on various forms of nitrosative stress (1).

Further reading: Vitamin B12 and Nitrosative Stress

The Benefits of Vitamin B12 for Skin

Even when used externally on the skin, vitamin B12 acts as a NO scavenger, which is why there are many vitamin B12 creams on sale. In 2009, B12 cream was trumpeted for some time as a “miracle cure” against eczema and psoriasis. Even so, the scientific evidence is still thin and the effect of B12 cream remains under question by many dermatologists, even though individual patients have reported successful results. Nevertheless, an internal consumption of B12 should have positive effects on skin diseases in certain cases – probably due to the role of the vitamin in tackling nitrogen oxides.

Vitamin B12 Benefits: An Inconspicuous Vitamin with a Mighty Effect

While other vitamins, such as C, D and E, have recently received lots of attention, vitamin B12 is still a somewhat inconspicuous vitamin. However, since evermore people are becoming vegetarian and vegan, B12 has earned significantly more recognition. This will probably increase in the long term, as the multiple benefits of vitamin B12 continue to surprise researchers. It is thus becoming increasingly clear that the vitamin plays a major role in both our physical and mental health.


  1. 1 Kuklinski, B.: Praxisrelevanz des nitrosativen Stresses. 1. Mitteilung: Diagnostik und Therapie neurologischer Erkran kungen. OM & Ernährung 124 (2008) F2 – F21
  2. 2 Ariel Miller, Maya Korem, Ronit Almog, Yanina Galboiz, Vitamin B12, demyelination, remyelination and repair in multiple sclerosis, Journal of the Neurological Sciences, Volume 233, Issues 1–2, 15 June 2005, Pages 93-97, ISSN 0022-510X,
  3. 3 Reynolds EH, Bottiglieri TT, Laundy MM, Crellin RF, Kirker SC. Vitamin B12 Metabolism in Multiple Sclerosis. Arch Neurol. 1992;49(6):649-652. doi:10.1001/archneur.1992.00530300089014.
  4. 4 Bottiglieri, T. (1996), Folate, Vitamin B12, and Neuropsychiatric Disorders. Nutrition Reviews, 54: 382–390. doi: 10.1111/j.1753-4887.1996.tb03851.x
  5. 5 Demise J. Subtle vitamin deficiency and psychiatry: A largely unnoticed and devastating relationship. Med Hypothesis. 1991;34:131–40
  6. 6 Tetsuya Watanabe, Ryuji Kaji, Nobuyuki Oka, William Bara, Jun Kimura, Ultra-high dose methylcobalamin promotes nerve regeneration in experimental acrylamide neuropathy, Journal of the Neurological Sciences, Volume 122, Issue 2, April 1994, Pages 140-143, ISSN 0022-510X,
  7. 7 B. Regland M. Andersson L. Abrahamsson J. Bagby L. E. Dyrehag C. G. Gottfries. Increased Concentrations of Homocysteine in the Cerebrospinal Fluid in Patients with Fibromyalgia and Chronic Fatigue Syndrome. Scandinavian Journal of Rheumatology 1997 26:4, 301-307
  8. 8 Martin L. Pall. Cobalamin Used in Chronic Fatigue Syndrome Therapy Is a Nitric Oxide Scavenger. Journal of Chronic Fatigue Syndrome 2000 8:2, 39-44
  9. 9 Hall, C. A. (1990), Function of vitamin B12 in the central nervous system as revealed by congenital defects. Am. J. Hematol., 34: 121–127. doi: 10.1002/ajh.2830340208
  10. 10 Casella EB, Valente M, de Navarro JM, Kok F. Vitamin B12 deficiency in infancy as a cause of developmental regression. Brain Dev. 2005 Dec;27(8):592-4. PubMed PMID: 16310594.
  11. 11 Karl-Olof Lövblad, Gianpaolo Ramelli, Luca Remonda, Arto C. Nirkko, Christoph Ozdoba, Gerhard Schroth. Retardation of myelination due to dietary vitamin B12 deficiency: cranial MRI findings. Pediatric Radiology February 1997, Volume 27, Issue 2, pp 155-158
  12. 12 K. Stollhoff, F. J. Schulte. Vitamin B12 and brain development. European Journal of Pediatrics March 1987, Volume 146, Issue 2, pp 201-205
  13. 13 Wighton MC, Manson JI, Speed I, Robertson E, Chapman E. Brain damage in infancy and dietary vitamin B12 deficiency. Med J Aust. 1979 Jul 14;2(1):1-3. PubMed PMID: 502936.
  14. 14 T. Lücke , G. C. Korenke , I. Poggenburg , K. H. P. Bentele , A. M. Das , H. Hartmann. Mütterlicher Vitamin-B12-Mangel: Ursache neurologischer Symptomatik im Säuglingsalter. Z Geburtshilfe Neonatol 2007; 211(4): 157-161
  15. 15 T. Kühne, R. Bubl, R. Baumgartner. Maternal vegan diet causing a serious infantile neurological disorder due to vitamin B12 deficiency. European Journal of Pediatrics January 1991, Volume 150, Issue 3, pp 205-208
  16. 16 Sklar R. Nutritional vitamin B12 deficiency in a breast-fed infant of a vegan-diet mother. Clin Pediatr (Phila). 1986 Apr;25(4):219-21. PubMed PMID: 3948463
  17. Karapiperi K, Gousis C and Papaioannidou P (2010). The role of vitamin B12 in DNA modulation mechanisms. Front. Pharmacol. Conference Abstract: 8th Southeast European Congress on Xenobiotic Metabolism and Toxicity – XEMET 2010.
  18. Thakkar, K., & Billa, G. (2015). Treatment of vitamin B12 deficiency–Methylcobalamine, Cyancobalamine, Hydroxocobalamin—clearing the confusion. European journal of clinical nutrition, 69(1), 1-2.
  19. A.G. Freeman Cyanocobalamin – a case for withdrawal: discussion paper. J R Soc Med. Nov 1992; 85(11): 686–687.

However, it’s also possible for you to struggle with a B12 deficiency even if you don’t have an underlying health condition. Strict vegetarians and vegans are also at a higher risk of developing a B12 deficiency than lacto-ovo vegetarians (vegetarians who still eat eggs and dairy products) and non-vegetarians, according to the NIH.

Gans says that if you’re not getting enough B12 on a regular basis, you could suffer from vitamin deficiency anemia, a condition in which your blood lacks enough healthy red blood cells. This can lead to numbness and tingling in your hands and feet, mental confusion, weight loss, and generally feeling wiped out and weak, as reported by the Mayo Clinic. If you suspect that you’re deficient in B12 Warren recommends that you talk to your doctor, who can order a blood test to help determine if that’s the case.

How can I add more B12 to my diet?

Most people get enough B12 from the foods they eat “without thinking about it,” Gans says. She points to animal products like beef, poultry, fish, eggs, and dairy as B12-rich items, adding that some foods — including breakfast cereals, some non-dairy beverages (like almond and soy milk), and meat substitutes — are fortified with it. “It’s best to read nutrition labels to check,” she says.

Of course, some foods have more B12 than others: The NIH reports that clams are packed with the vitamin at 84.1 micrograms per three-ounce serving, while liver also contains a fair amount. But again, if you’re a vegan or follow a strict vegetarian diet, it can be hard to get enough B12 in your diet.

What are B12 injections, and should I try them?

Yes, B12 injections may have had a moment in the spotlight, but it’s not really advisable (or necessary) for the average person, Keatley says. If you’re not getting enough B12 in your diet, injections may be helpful; if you are, they’re unlikely to do anything. What’s more, being deficient in B12 doesn’t mean you automatically have to have regular shots since some people do just fine with supplements in pill form, Keatley says. But if you have pernicious anemia (that is caused by a B12 deficiency) or have any other trouble absorbing B12, injections might be a good idea for you, Warren says.

What happens if you get too much B12?

If you’re taking B12 supplements and you accidentally take more than one in a day, nothing bad is going to happen to you. “Since B12 is a water-soluble vitamin, there really is no such thing as too much,” Gans says. “Your body will use what it wants and eliminate the rest.”

If you’re interested in taking a B12 supplement, it’s a good idea to talk to your doctor first because B12 supplements can interact with some medications like chloramphenicol (a type of antibiotic) and metformin (which is used to treat diabetes) or simply may not be necessary for you. A conversation with your doctor should help steer you in the right direction.

If you discover that you are B12 deficient, your doctor will determine how much extra B12 you need, as well as which supplement will work for you. Here are a few to consider.

Courtesy of brand

If you like your vitamins with a little flavor, check out this cherry formula, which is suitable for vegans and vegetarians alike. You can dissolve these lozenges on your tongue or chew them.

$6 (Shop Now)

Courtesy of brand

If gummies are more your style, then Nature Made makes some admittedly delicious fruit-flavored ones. Keep in mind that these contain gelatin, which isn’t an acceptable ingredient for vegetarians.

$14 (Shop Now)

Courtesy of brand

If you’re looking for something simple, Nature’s Bounty has you covered with these vegetarian-friendly tablets, which are free of artificial flavors and colors and coated for easy swallowing.

$12 (Shop Now)

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Are you a new drug developer? Contact us to learn more about our customized products and solutions. Stay in the know! As part of our commitment to providing the most up-to-date drug information, we will be releasing #DrugBankUpdates with our newly added curated drug pages. #DrugBankUpdates Name Cyanocobalamin
Commonly known or available as Vitamin B12 Accession Number DB00115 (NUTR00004, APRD00326, EXPT00965) Type Small Molecule Groups Approved, Nutraceutical Description

Cyanocobalamin (commonly known as Vitamin B12) is a highly complex, essential vitamin, owing its name to the fact that it contains the mineral, cobalt. This vitamin is produced naturally by bacteria 16, and is necessary for DNA synthesis and cellular energy production. Vitamin B12 has many forms, including the cyano-, methyl-, deoxyadenosyl- and hydroxy-cobalamin forms. The cyano form, is the most widely used form in supplements and prescription drugs 10, Label. Several pharmaceutical forms of cyanocobalamin have been developed, including the tablet, injection, and nasal spray forms Label, 19, 20. This drug was initially approved by the FDA in 1942 Label.

Structure Download Similar Structures

Structure for Cyanocobalamin (DB00115)

× Close Synonyms

  • Cianocobalamina
  • Cyanocob(III)alamin
  • Cyanocobalamin
  • Cyanocobalamine
  • Cyanocobalaminum
  • Vitamin B12
  • Vitamin B12 complex
  • Vitamin B12 NOS

Product Images Prescription Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
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B-12 1000 Inj 1000mcg/ml Solution Intramuscular; Subcutaneous Omega Laboratories Ltd 1985-12-31 Not applicable Canada
Bedoz 1000inj Liquid Intramuscular Lab Nadeau LtÉe, Division Of Technilab Inc. 1951-12-31 2005-08-05 Canada
CaloMist Spray, metered 25 ug/0.1mL Nasal Fleming & Company, Pharmaceuticals 2007-10-01 2010-01-26 US
Cobex Inj 1000mcg/ml Solution Intramuscular; Subcutaneous Kripps Pharmacy Ltd. 1979-12-31 Not applicable Canada
Crystalline Vitamin B12-liq Im Sc 1000mcg/ml Liquid Intramuscular; Subcutaneous Germiphene Corporation 1996-12-31 1999-06-28 Canada
Cyanocobalamin Injection USP Solution Intramuscular; Subcutaneous Teligent Ou Not applicable Not applicable Canada
Cyanocobalamin Injection USP Solution Intramuscular; Subcutaneous Sterimax Inc 1992-12-31 Not applicable Canada
Cyanocobalamin Injection USP Liquid Intramuscular; Subcutaneous Teligent Ou 2018-01-16 Not applicable Canada
Cyanocobalamin Injection USP 1000mcg/ml Liquid Intramuscular; Subcutaneous Taro Pharmaceuticals, Inc. 1987-12-31 Not applicable Canada
Cyanocobalamin Injection, USP Solution Intramuscular; Subcutaneous Mylan Pharmaceuticals 2014-07-25 Not applicable Canada

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  • Product Code Product Code

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Generic Prescription Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
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Aj-cyanocobalamin Solution Intramuscular; Subcutaneous Agila Jamp Canada Inc Not applicable Not applicable Canada
B12 Inject Kit Kit 1000 ug/1mL Intramuscular; Subcutaneous Oaklock, Llc 2015-06-19 Not applicable US
B12 Inject Kit Kit 1000 ug/1mL Intramuscular Oaklock, Llc 2015-07-08 Not applicable US
Cyanocobalamin Injection, solution 1000 ug/1mL Intramuscular; Subcutaneous Mc Kesson Packaging Services A Buisness Unit Of Mc Kesson Corporation 2010-02-01 2012-02-24 US
Cyanocobalamin Injection 1000 ug/1mL Intramuscular; Subcutaneous Somerset Therapeutics, Llc 2015-12-11 Not applicable US
Cyanocobalamin Injection, solution 1000 ug/1mL Intramuscular Ubi Pharma Inc. 2019-01-02 Not applicable US
Cyanocobalamin Injection, solution 1000 ug/1mL Intramuscular; Subcutaneous Fresenius Kabi USA, LLC 2000-10-18 Not applicable US
Cyanocobalamin Injection, solution 1000 ug/1mL Intramuscular General Injectables & Vaccines 2010-03-01 Not applicable US
Cyanocobalamin Injection 1000 ug/1mL Intramuscular; Subcutaneous General Injectables and Vaccines, Inc. 2018-07-20 Not applicable US
Cyanocobalamin Injection, solution 1000 ug/1mL Intramuscular; Subcutaneous Somerset Therapeutics, Llc 2018-12-18 Not applicable US

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Over the Counter Products

Name Dosage Strength Route Labeller Marketing Start Marketing End
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B-12 1000mcg Continuous Released Tab Tablet, extended release Oral Gahler Enterprises Ltd. 1981-12-31 2000-10-03 Canada
B-plex Tablet Oral Beverly International Nutrition 1986-12-31 1998-08-01 Canada
B12 1000mcg Tablet Oral Natural Factors Nutritional Products Ltd. 2000-09-01 2007-08-07 Canada
B12 250mcg Cyanocobalamin Tablet Oral Wn Pharmaceuticals Ltd. 2001-10-01 2009-09-28 Canada
Coco12 Lotion 0.05 g/0.05g Topical Scientfic Solutions Global LLC 2019-09-26 Not applicable US
Forphyll 3mcg Tablet Oral Therapeutic Foods Co. 1989-12-15 2004-07-22 Canada
Gsf Tab 24mcg Tablet Oral Nutri Dyn Products Ltd. 1980-12-31 1996-09-09 Canada
Puro Sang Tab 1mcg Tablet Oral Pharmetics (2011) Inc. 1966-12-31 2001-07-26 Canada
Vit B12 Ctr Srt 1200mcg Tablet, extended release Oral Bioenergy Inc. 1979-12-31 1998-06-03 Canada
Vit B12 Tab 500mcg Tablet Oral Pure Life International Prods Inc. 1992-12-31 2001-08-07 Canada

Additional Data Available

  • Application Number Application Number

    A unique ID assigned by the FDA when a product is submitted for approval by the labeller.

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  • Product Code Product Code

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Mixture Products Unapproved/Other Products International/Other Brands Bedodeka (Teva) / Bedoz / Berubigen (Upjohn) / Betalin (Lilly) / Cobione (MSD) / Cobolin-M / Crystamine / Cyanoject / Cyomin / Cytakon (GlaxoSmithKline) / Cytamen (GlaxoSmithKline) / Dicopac / Neuroforte-R / Primabalt / Vitabee 12 Categories UNII P6YC3EG204 CAS number 68-19-9 Weight Average: 1355.3652
Monoisotopic: 1354.5674053 Chemical Formula C63H88CoN14O14P InChI Key RMRCNWBMXRMIRW-WZHZPDAFSA-L InChI InChI=1S/C62H90N13O14P.CN.Co/c1-29-20-39-40(21-30(29)2)75(28-70-39)57-52(84)53(41(27-76)87-57)89-90(85,86)88-31(3)26-69-49(83)18-19-59(8)37(22-46(66)80)56-62(11)61(10,25-48(68)82)36(14-17-45(65)79)51(74-62)33(5)55-60(9,24-47(67)81)34(12-15-43(63)77)38(71-55)23-42-58(6,7)35(13-16-44(64)78)50(72-42)32(4)54(59)73-56;1-2;/h20-21,23,28,31,34-37,41,52-53,56-57,76,84H,12-19,22,24-27H2,1-11H3,(H15,63,64,65,66,67,68,69,71,72,73,74,77,78,79,80,81,82,83,85,86);;/q;;+2/p-2/t31-,34-,35-,36-,37+,41-,52-,53-,56-,57+,59-,60+,61+,62+;;/m1../s1 IUPAC Name cyanooxy}propyl]carbamoyl}ethyl)-1,4,6,9,9,14,16,19-octamethyl-20,21,22,23-tetraazapentacyclotricosa-5(23),6,10(22),11,15(21),16-hexaen-20-yl]cobaltylium SMILES C(CNC(=O)CC1(C)(CC(N)=O)2N=C1\C(C)=C1/N=C(/C=C3\N=C(\C(\C)=C4\(CCC(N)=O)(C)(CC(N)=O)2(C)N4C#N)(C)(CC(N)=O)3CCC(N)=O)C(C)(C)1CCC(N)=O)OP()(=O)O1(CO)O(1O)N1C=NC2=C1C=C(C)C(C)=C2



Nasal spray

The cyanocobalamin nasal spray is indicated for the maintenance of vitamin B12 concentrations after normalization with intramuscular vitamin B12 therapy in patients with deficiency of this vitamin who have no nervous system involvement Label.

Note: CaloMist Label, the nasal spray form, has not been evaluated for the treatment of newly diagnosed vitamin B12 deficiency.

Injection forms (subcutaneous, intramuscular)

These forms are indicated for vitamin B12 deficiencies due to various causes, with or without neurologic manifestations 26. Vitamin B12 deficiency is frequently caused by malabsorption, which is often associated with the following conditions 20:

Addisonian (pernicious) anemia

Gastrointestinal pathology, dysfunction, or surgery, including gluten enteropathy or sprue, small bowel bacterial overgrowth, total or partial gastrectomy

Fish tapeworm infestation

Malignancy of the pancreas or bowel

Folic acid deficiency

Oral forms

Vitamin B12 supplements are widely available and indicated in patients who require supplementation for various reasons. Dose requirements for vitamin B12 which are higher than normal (caused by pregnancy, thyrotoxicosis, hemolytic anemia, hemorrhage, malignancy, hepatic and renal disease) can usually be achieved with oral supplementation 20. Oral products of vitamin B12 are not recommended in patients with malabsorption, as these forms are primarily absorbed in the gastrointestinal tract 27.

Associated Conditions

  • Anemia, Pernicious
  • Vitamin B12 Deficiency
  • Vitamin B12 concentration


General effects

Cyanocobalamin corrects vitamin B12 deficiency and improves the symptoms and laboratory abnormalities associated with pernicious anemia (megaloblastic indices, gastrointestinal lesions, and neurologic damage). This drug aids in growth, cell reproduction, hematopoiesis, nucleoprotein, and myelin synthesis. It also plays an important role in fat metabolism, carbohydrate metabolism, as well as protein synthesis. Cells that undergo rapid division (for example, epithelial cells, bone marrow, and myeloid cells) have a high demand for vitamin B12 10.

Parenteral cyanocobalamin effects

The parenteral administration of vitamin B12 rapidly and completely reverses the megaloblastic anemia and gastrointestinal symptoms of vitamin B12 deficiency. Rapid parenteral administration of vitamin B12 in deficiency related neurological damage prevents the progression of this condition 20.

Nasal spray effects

In 24 vitamin B12 deficient patients who were already stabilized on intramuscular (IM) vitamin B12 therapy, single daily doses of intranasal cyanocobalamin for 8 weeks lead to serum vitamin B12 concentrations that were within the target therapeutic range (>200 ng/L) Label.

Mechanism of action

Vitamin B12 serves as a cofactor for methionine synthase and L-methylmalonyl-CoA mutase enzymes. Methionine synthase is essential for the synthesis of purines and pyrimidines that form DNA. L-methylmalonyl-CoA mutase converts L-methylmalonyl-CoA to succinyl-CoA in the degradation of propionate 24, an important reaction required for both fat and protein metabolism. It is a lack of vitamin B12 cofactor in the above reaction and the resulting accumulation of methylmalonyl CoA that is believed to be responsible for the neurological manifestations of B12 deficiency 10. Succinyl-CoA is also necessary for the synthesis of hemoglobin 24.

In tissues, vitamin B12 is required for the synthesis of methionine from homocysteine. Methionine is required for the formation of S-adenosylmethionine, a methyl donor for nearly 100 substrates, comprised of DNA, RNA, hormones, proteins, as well as lipids 24. Without vitamin B12, tetrahydrofolate cannot be regenerated from 5-methyltetrahydrofolate, and this can lead to functional folate deficiency 22, Label. This reaction is dependent on methylcobalamin (vitamin B12) as a co-factor and is also dependent on folate, in which the methyl group of methyltetrahydrofolate is transferred to homocysteine to form methionine and tetrahydrofolate. Vitamin B12 incorporates into circulating folic acid into growing red blood cells; retaining the folate in these cells 23. A deficiency of vitamin B12 and the interruption of this reaction leads to the development of megaloblastic anemia.

Target Actions Organism
AMethionine synthase cofactor Humans
AMethylmalonyl-CoA mutase, mitochondrial cofactor Humans
UMethionine synthase reductase cofactor Humans
UMethylmalonic aciduria type A protein, mitochondrial binder Humans
UMethylmalonic aciduria and homocystinuria type C protein cofactor Humans
UMethylenetetrahydrofolate reductase cofactor Humans

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Learn more Absorption

Vitamin B12 is quickly absorbed from intramuscular (IM) and subcutaneous (SC) sites of injection; with peak plasma concentrations achieved about 1 hour after IM injection 26.

Orally administered vitamin B12 binds to intrinsic factor (IF) during its transport through the stomach. The separation of Vitamin B12 and IF occurs in the terminal ileum when calcium is present, and vitamin B12 is then absorbed into the gastrointestinal mucosal cells. It is then transported by transcobalamin binding proteins 20. Passive diffusion through the intestinal wall can occur, however, high doses of vitamin B12 are required in this case (i.e. >1 mg). After the administration of oral doses less than 3 mcg, peak plasma concentrations are not reached for 8 to 12 hours, because the vitamin is temporarily retained in the wall of the lower ileum 26.

Volume of distribution

Cobalamin is distributed to tissues and stored mainly in the liver and bone marrow Label.

Protein binding

Very high (to specific plasma proteins called transcobalamins); binding of hydroxocobalamin is slightly higher than cyanocobalamin

  • Erdogan MO, Yildiz SH, Solak M, Eser O, Cosar E, Eser B, Koken R, Buyukbas S: C677T polymorphism of the methylenetetrahydrofolate reductase gene does not affect folic acid, vitamin B12, and homocysteine serum levels in Turkish children with neural tube defects. Genet Mol Res. 2010 Jun 22;9(2):1197-203. doi: 10.4238/vol9-2gmr816.
  • Enzymes

    Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Cob(i)yrinic acid a,c-diamide adenosyltransferase activity Specific Function Not Available Gene Name MMAB Uniprot ID Q96EY8 Uniprot Name Cob(I)yrinic acid a,c-diamide adenosyltransferase, mitochondrial Molecular Weight 27387.975 Da

    1. Zhang J, Dobson CM, Wu X, Lerner-Ellis J, Rosenblatt DS, Gravel RA: Impact of cblB mutations on the function of ATP:cob(I)alamin adenosyltransferase in disorders of vitamin B12 metabolism. Mol Genet Metab. 2006 Apr;87(4):315-22. Epub 2006 Jan 24.
    2. Lerner-Ellis JP, Gradinger AB, Watkins D, Tirone JC, Villeneuve A, Dobson CM, Montpetit A, Lepage P, Gravel RA, Rosenblatt DS: Mutation and biochemical analysis of patients belonging to the cblB complementation class of vitamin B12-dependent methylmalonic aciduria. Mol Genet Metab. 2006 Mar;87(3):219-25. Epub 2006 Jan 10.

    Kind Protein Organism Salmonella typhimurium (strain LT2 / SGSC1412 / ATCC 700720) Pharmacological action Unknown Actions Product of General Function Gtp binding Specific Function Catalyzes ATP-dependent phosphorylation of adenosylcobinamide and addition of GMP to adenosylcobinamide phosphate. Gene Name cobU Uniprot ID Q05599 Uniprot Name Bifunctional adenosylcobalamin biosynthesis protein CobU Molecular Weight 19901.7 Da 3. Pancreatic proteases Kind Group Organism Not Available Pharmacological action Unknown Actions SubstrateThis group is comprised of proteases secreted from the pancreas.


    Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Receptor binding Specific Function Necessary for efficient absorption of vitamin B12. May direct the production of trunk mesoderm during development by modulating a bone morphogenetic protein (BMP) signaling pathway in the underlyin… Gene Name AMN Uniprot ID Q9BXJ7 Uniprot Name Protein amnionless Molecular Weight 47753.91 Da Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Cobalamin binding Specific Function Binds vitamin B12 with femtomolar affinity and protects it from the acidic environment of the stomach. Gene Name TCN1 Uniprot ID P20061 Uniprot Name Transcobalamin-1 Molecular Weight 48206.32 Da Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Metal ion binding Specific Function Primary vitamin B12-binding and transport protein. Delivers cobalamin to cells. Gene Name TCN2 Uniprot ID P20062 Uniprot Name Transcobalamin-2 Molecular Weight 47534.54 Da Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Cobalamin binding Specific Function Promotes absorption of the essential vitamin cobalamin (Cbl) in the ileum. After interaction with CUBN, the GIF-cobalamin complex is internalized via receptor-mediated endocytosis. Gene Name GIF Uniprot ID P27352 Uniprot Name Gastric intrinsic factor Molecular Weight 45415.67 Da Details5. Cubilin Kind Protein Organism Humans Pharmacological action Unknown Actions Substrate General Function Transporter activity Specific Function Cotransporter which plays a role in lipoprotein, vitamin and iron metabolism, by facilitating their uptake. Binds to ALB, MB, Kappa and lambda-light chains, TF, hemoglobin, GC, SCGB1A1, APOA1, high… Gene Name CUBN Uniprot ID O60494 Uniprot Name Cubilin Molecular Weight 398732.93 Da Kind Protein Organism Humans Pharmacological action Unknown General Function Calcium ion binding Specific Function Acts together with cubilin to mediate HDL endocytosis (By similarity). May participate in regulation of parathyroid-hormone and para-thyroid-hormone-related protein release. Gene Name LRP2 Uniprot ID P98164 Uniprot Name Low-density lipoprotein receptor-related protein 2 Molecular Weight 521952.77 Da Kind Protein Organism Humans Pharmacological action Unknown General Function Transporter activity Specific Function Mediates export of organic anions and drugs from the cytoplasm. Mediates ATP-dependent transport of glutathione and glutathione conjugates, leukotriene C4, estradiol-17-beta-o-glucuronide, methotre… Gene Name ABCC1 Uniprot ID P33527 Uniprot Name Multidrug resistance-associated protein 1 Molecular Weight 171589.5 Da ×Unlock Data

    There is additional data available for commercial users including Adverse Effects, Contraindications, and Blackbox Warnings. Contact us to learn more about these and other features.

    Learn more

    Drug created on June 13, 2005 07:24 / Updated on February 02, 2020 00:09

    Evolving Wellness


    I want to take B12 supplements and I understand that Methylcobalamin is a better choice when compared to Cyanocobalamin, since the body doesn’t have to convert to be useable and this form already exists in nature. What I am not sure about is what brand to choose and what B12 supplement form is more effective, pill or liquid?



    Yes, I definitely recommend to go with the methylcobalamin form of B12 over the cyanocobalamin form for most people’s common usage of this supplement. Methylcobalamin is the natural and active form of this vitamin, whereas cyanocobalamin is synthetic, it does not exist in nature and is chemically-derived, and much cheaper to produce, which is mainly why most vitamin B12 supplements contain it. There are certain health cases that may warrant the use of cyanocobalamin or even another form of B12 altogether, but these usually apply to people who have problems digesting or assimilating vitamin B12 or suffer from serious deficiencies of it. For more information read the following article about methylcobalamin versus cyanocobalamin use.

    With regards to the best brands of B12 methylcobalamin, there are hundreds, if not thousands, of supplement brands worldwide, and most vary in availability by region in the world. It is therefore difficult to recommend a specific brand for any number of logistical reasons. Over the years I have personally cycled through many brands, and as my research and awareness grew and as supplement formulas change, I have never been able to stick with one brand that I can routinely rely on. The most important advice I follow and recommend to others is to, first, rely on supplements as little as possible. Nothing in a bottle, no formula or supplement, will ever be truly risk-free or be able to fully replace what only whole natural plant food is capable of providing. To understand this further, I recommend the following video episode I did with Dr. John McDougall about supplements and plant-based eating.

    The second most important advice I live by and recommend to others, when it comes to supplements, is to seek products that are are pure and high quality as possible. This means that you always read the other ingredients listed on the bottle and determine whether you feel comfortable with those ingredients. It is here that we will usually find all sorts of animal by-products, colors, flavors, artificial sweeteners, fillers, GMOs, allergens, and preservatives. At minimum, any supplement we choose should be vegan, with no gelatin or any other animal-derived ingredients, and free of such harmful ingredients. After that, it may be necessary to sacrifice a little, where a formula may contain some natural flavor or sugar alcohols, like xylitol. Neither of these are high risk ingredients, and will usually be found in negligible amounts anyway in supplements. Organic supplements, especially when they contain whole food parts, can be a big asset, but it is not always easy to tell if they include what they claim to include or whether it is even significant. Other than that, it is next to impossible to find a truly “pure” supplement, and why, aside from vitamin B12, the less we depend on them, the better.

    Ingredients aside, to determine whether the supplement is of a true high quality, specifically when it comes to potency and efficacy, it takes a little research. Don’t fall for any of the claims on the package or the product website. Marketing can bend rules like crazy and make all sorts of claims, and given that supplements are very poorly regulated in most countries, consumers are most often left in the dark about the quality of the product they are using. Remember, image sells and is highly persuasive given our emotional tendency to make decisions. So just because a brand comes across as pure, natural, or high quality, does not mean it is.

    When it comes to effectiveness, both a pill and a liquid can be sublingual, and thus contain the methylcobalamin form of B12. Similarly, both a pill and a liquid of B12 methylcobalamin can be non-sublingual and made to be swallowed. Given the characteristics of methylcobalamin, in terms of how readily it cab be absorbed by our body and how much it can be destroyed going through the digestive tract, I most recommend sublingual forms of it. But from amongst the methyl sublingual forms, there won’t be much difference between a dissolvable pill and a liquid, as long as the tablet dissolves well. In this case, I would recommend to pick either a pill or liquid sublingual form based on what is personally preferred.

    Top Choices of Vitamin B12 Methylcobalamin Brands

    All of the following choices are suitable for vegans and are the purest formulas available with no harmful ingredients, like animal by-products, GMOs, preservatives, colors/dyes, artificial flavors, or common allergens. They are listed in alphabetical order, and not in any order of preference. Note that this list is not exhaustive of all of the possible good choices out there; it is focused on brands that I am familiar with that are common in Canada and the United States. Formulas may change at any time, so be sure to read the ingredients of the actual product package you are interested in before buying. Any product chosen should be based on what you feel would be the best choice for you, taking into consideration the supplement form, dose, flavor, price, and availability in your area.

    Deva Vegan Vitamins

    Product: B12 Methylcobalamin 1,000 mcg Lemon Tablets — sublingual
    Features: With vitamin B6 and folate
    Other Ingredients: Xylitol, Mannitol, Lemon Flavor, Crospovidone, Citric Acid, Sodium Citrate, Vegetable Magnesium Stearate, Silica. (All from non-animal sources.)
    Product: B12 Methylcobalamin 2,500 mcg Lemon Tablets — sublingual
    Other Ingredients: Xylitol, Mannitol, Lemon Flavor, Crospovidone, Citric Acid, Sodium Citrate, Vegetable Magnesium Stearate, Silica. (All from non-animal sources.)

    Live Wise Naturals

    Product: B12 Methylcobalamin Liquid — sublingual
    Features: Flexible dosage from 200mcg to 6,000mcg (depending on number of drops taken)
    Other Ingredients: Purified Water, Organic Grape Alcohol, Monoammonium Glycyrrhizinate (Licorice Root Isolate).


    Product: Methyl B12 500 mcg Tablets — not sublingual
    Features: With methylated folate and vitamin B6, with red beet root, broccoli, and brown rice.
    Other Ingredients: Cellulose, Stearic Acid, Silica.

    New Roots Herbal

    Product: B12 Methylcobalamin 1,000mcg Capsules — not sublingual
    Features: With red beet root, dandelion root, lapacho bark, and plant enzymes.
    Other Ingredients: Vegetable Magnesium Stearate, Silicon dioxide, Vegetable Capsule (Vegetable Carbohydrate Gum, Purified water).

    Pure Encapsulations

    Product: B12 Methylcobalamin 1,000 mcg Capsules — not sublingual
    Other Ingredients: Hypoallergenic Plant Fiber (Cellulose), Vegetarian Capsule (Cellulose, Water)


    Product: B12 Methylcobalamin 1,000 mcg Cherry Nuggets — sublingual
    Other Ingredients: Mannitol, Vegetable Stearic Acid, Silica, Vegetable Magnesium Stearate, Natural Cherry Flavor, Vegetable Cellulose.
    Product: B12 Methylcobalamin 2,500 mcg Cherry Nuggets — sublingual
    Other Ingredients: Mannitol, Vegetable Stearic Acid, Vegetable Magnesium Stearate, Natural Cherry Flavor, Silica.
    Product: B12 Methylcobalamin 5,000 mcg Cherry Nuggets — sublingual
    Other Ingredients: Mannitol, Microcrystalline Cellulose, Vegetable Stearic Acid, Silica, Natural Cherry Flavor, Vegetable Cellulose, Vegetable Magnesium Stearate.


    Product: B12 Methylcobalamin 1,000 mcg Lemon Lozenges — sublingual
    Other Ingredients: Xylitol, Cellulose, Stearic Acid (Vegetable Source), Natural Lemon Flavor, Magnesium Stearate (Vegetable Source), Citric Acid, Silicon Dioxide.
    Product: B12 Methylcobalamin 2,500 mcg Tropical Lozenges — sublingual
    Other Ingredients: Xylitol, Cellulose, Natural Tropical Flavor, Ascorbic acid, Stearic Acid (Vegetable Source), Silicon Dioxide.
    Product: B12 Methylcobalamin 5,000 mcg Cherry Lozenges — sublingual
    Other Ingredients: Xylitol, Cellulose, Stearic Acid (Vegetable Source), Natural Cherry Flavor, Citric Acid, Magnesium Stearate (Vegetable Source).

    Other Brands

    Two other brands that also specialize in organic, pure, and whole food forms of supplements are New Chapter and Garden of Life. However, New Chapter does not have a specific B12 methylcobalamin formula. The closest they have is their Coenzyme B Food Complex, which contains all the B vitamins, and B12 in the cyanocobalamin form. Garden of Life does have a B12 methylcobalamin liquid and B12 methylcobalamin capsule, but I cannot recommend their products anymore, since they became acquired by Nestle at the end of 2017. Given Nestle’s slew of unethical practices and harmful products, Garden of Life products will not be a good choice for conscientious consumers who care what company they support with their money and want to ensure that a company’s values are in alignment with the greater good of all. Sadly, most natural supplement brands are owned by large corporations that often work directly against our health and wellbeing, so it has become increasingly challenging to make truly ethical choices today. This is where a little care, research, and awareness can go a long way to not only get a good product but also support the right companies with your money too.

    In the end, when it comes to any supplements the most important thing is to avoid the common, conventional and generic brands that have supplement formulas full of various risky, harmful, and allergenic ingredients. There is no need to sacrifice your health when there are so many better and safer alternative choices today.

    For more information about vitamin B12 in general, why it is important and where it comes from in nature, please refer to: Vitamin B12 Questions Answered from Forks Over Knives.

    Vitamin B12 Side Effects

    Generic Name: cyanocobalamin

    Medically reviewed by Last updated on Dec 29, 2018.

    • Overview
    • Side Effects
    • Dosage
    • Interactions
    • Pregnancy
    • Reviews
    • More

    Note: This document contains side effect information about cyanocobalamin. Some of the dosage forms listed on this page may not apply to the brand name Vitamin B12.

    For the Consumer

    Applies to cyanocobalamin: intramuscular solution

    Other dosage forms:

    • nasal spray

    Along with its needed effects, cyanocobalamin (the active ingredient contained in Vitamin B12) 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 or nurse immediately if any of the following side effects occur while taking cyanocobalamin:

    Incidence not known

    • Abdominal or stomach pain
    • bleeding from the gums or nose
    • blue lips and fingernails
    • chest pain
    • cough
    • coughing that sometimes produces a pink frothy sputum
    • decreased urine output
    • difficult, fast, noisy breathing, sometimes with wheezing
    • difficulty with swallowing
    • dilated neck veins
    • dizziness
    • extreme fatigue
    • eye pain
    • fast heartbeat
    • headache
    • hives, itching, or skin rash
    • increased sweating
    • irregular breathing
    • irregular heartbeat
    • pale skin
    • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
    • ringing in the ears
    • swelling of the face, fingers, feet, or lower legs
    • tightness in the chest
    • unusual tiredness or weakness
    • weight gain

    Some side effects of cyanocobalamin 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:

    Incidence not known

    • Diarrhea
    • skin rash with a general disease

    For Healthcare Professionals

    Applies to cyanocobalamin: compounding powder, injectable solution, intramuscular solution, nasal gel, nasal spray, oral tablet, oral tablet extended release, sublingual lozenge, sublingual tablet


    Frequency not reported: Congestive heart failure, peripheral vascular thrombosis, cardiac arrest, low blood pressure


    Patients sensitized to the injectable product are often able to tolerate the oral route without problems.

    Frequency not reported: Anaphylactic shock and death, allergic hypersensitivity reactions


    Frequency not reported: Mild transient diarrhea, prolonged abdominal pain, prolonged nausea or vomiting

    Nervous system

    Frequency not reported: Severe dizziness, drowsiness, muscular paralysis, loss of consciousness


    Frequency not reported: Itching, transitory exanthema, acneiform eruptions, bullous eruptions


    Frequency not reported: Pulmonary edema


    Frequency not reported: Hypokalemia


    Frequency not reported: Polycythemia vera


    Frequency not reported: Vision problems


    Frequency not reported: Feeling of swelling of entire body

    1. Cerner Multum, Inc. “Australian Product Information.” O 0

    2. “Product Information. Cyanocobalamin (cyanocobalamin).” West-Ward Pharmaceutical Corporation, Eatontown, NJ.

    3. Cerner Multum, Inc. “UK Summary of Product Characteristics.” O 0

    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 Vitamin B12 (cyanocobalamin)

    • During Pregnancy
    • Dosage Information
    • Drug Interactions
    • Compare Alternatives
    • Support Group
    • 16 Reviews
    • Drug class: vitamins

    Consumer resources

    • Vitamin B-12 injection

    Other brands: Nascobal, Neuroforte-R, B-12 Dots, CaloMist, … +4 more

    Professional resources

    • Cyanocobalamin (FDA)

    Related treatment guides

    • Vitamin B12 Deficiency
    • Pernicious Anemia
    • B12 Nutritional Deficiency
    • Schilling Test

    by Jack Norris, RD


    • Summary
    • General Safety
    • Case Reports
    • Safety of Cyanocobalamin
    • Cyanocobalamin and Kidney Disease


    A few cases of rosacea and acneiform brought on by vitamin B12 treatment have been reported in the literature since the 1970s. Few people respond in this way, but if you notice a rash after taking large doses of vitamin B12, discontinue and follow the recommendations for using fortified foods or much smaller amounts of vitamin B12.

    General Safety

    It is generally believed that large doses of vitamin B12 are not harmful. The general consensus is summed up by Oregon State University’s Linus Pauling Institute, “No toxic or adverse effects have been associated with large intakes of vitamin B12 from food or supplements in healthy people. Doses as high as 1 mg (1000 mcg) daily by mouth or 1 mg monthly by intramuscular (IM) injection have been used to treat pernicious anemia without significant side effects.”

    No adverse effects were reported in a 12-week vitamin 12 supplementation study in which 14 people took a 2,000 µg dose of cyanocobalamin per week and a different 18 people took a daily dose of 50 µg (Del Bo’, 2019). The subjects all started with mild B12 deficiency, and all supplements were taken sublingually, i.e., dissolving under the tongue.

    Case Reports

    We have received a few reports from people who said they had a reaction to a high dose vitamin B12 supplement (typically 1,000 micrograms). Additionally, there have been numerous case reports in the literature, the most recent being from 2001:

    A 17-year old female in Germany had an outbreak of rosacea fulminans two weeks after starting a daily regimen of taking 80 mg of vitamin B6 and 20 micrograms of vitamin B12 (Jansen, 2001). These amounts are not unusually large.

    A diagnosis of “rosacea fulminans related to vitamin B excess” was made, and the girl was instructed to discontinue use of the nutritional supplement and treated with methylprednisolone, isotretinoin, and clobetasol propionate which led to resolution of all skin changes within 4 months, with no residual scarring.

    The authors wrote, “Vitamins B2 (riboflavin), B6 (pyridoxine) and B12 (cyanocobalamin) are known to be capable of exacerbating acne or precipitating acneiform eruptions.”

    A 1991 case report from North Carolina says “This case illustrates an eruption resembling acne rosacea that was temporally associated with daily ingestion of high-dose B vitamin supplement. The eruption failed to respond to the usual treatment regimens for rosacea, but promptly improved when use of the vitamin supplement was discontinued.” (Sherertz, 1991)

    The abstract to a German article says that 14 patients developed acne from treatment with vitamin B6 and/or vitamin B12 (Braun-Falco, 1976). Amounts were not given in the abstract.

    Safety of Cyanocobalamin

    The safety of cyanocobalamin has raised concerns due to the fact that cyanide is a component of cyanocobalamin, and the cyanide molecule is removed from cyanocobalamin when used by the body’s cells. Cyanide is also found in many fruits and vegetables and so humans are always ingesting small amounts of cyanide, and like in most fruits and vegetables, the amount of cyanide in cyanocobalamin is considered to be physiologically insignificant.

    According to the European Food Safety Authority, “Data of from a Norwegian dietary survey show that the average and high (97.5th percentile) daily intake of among consumers amounts to respectively 95 and 372 micrograms/person or 1.4 and 5.4 micrograms/kg bw/day (7).” The amount of cyanide in a 1,000 microgram cyanocobalamin tablet is 20 micrograms.

    Table 1 contains some additional numbers regarding cyanide amounts in cyanocobalamin for comparison purposes.

    Table 1. Cyanide Content of Cyanocobalamin
    molecular weight of vitamin B12 1,355 g/mol
    molecular weight of cyanide 27 g/mol
    Percentage of cyanide in vitamin B12 by weight 2.0%
    Amount of cyanide in 1,000 micrograms of cyanocobalamin 20 micrograms
    Minimal Risk Level for oral cyanide4, a 0.05 mg/kg of body weight per day
    Minimal Risk Level for oral cyanide for 140 lb person 3,175 micrograms/day
    Lethal dose of cyanide5 0.5 to 3.0 mg/kg of body weight
    Lower end of lethal dose of cyanide for 140 lb person 31,750 micrograms
    Percentage of lethal dose for a 140 lb person in 1,000 micrograms of cyanocobalamin 0.06%
    aMinimal Risk Level do not assess cancer risk (6).

    Cyanocobalamin and Kidney Disease

    People with kidney problems should not take large doses of cyanocobalamin, as they often cannot metabolize the cyanide efficiently. For more information, please see the Conditions that Contraindicate Cyanocobalamin.

    Last updated February 2012
    1. Jansen T, Romiti R, Kreuter A, Altmeyer P. Rosacea fulminans triggered by high-dose vitamins B6 and B12. J Eur Acad Dermatol Venereol. 2001 Sep;15(5):484-5.

    2. Sherertz EF. Acneiform eruption due to “megadose” vitamins B6 and B12. Cutis. 1991 Aug;48(2):119-20. Abstract.

    4. ToxGuide for Cyanide. Agency for Toxic Substances and Disease Registry. Centers for Disease Control. July 2006. Accessed 2/7/2012.

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