Fasting blood test coffee


Coffee Before Cholesterol Testing

I had a few cups of black coffee (no cream or sugar) before a cholesterol test. Will it affect the results, and if so, how? Can I have any liquids besides water before this test?

— Vicki, Michigan

Knowing your total cholesterol number and the values of its two components (HDL and LDL) can help you understand your risk for cardiovascular disease and allow you to make lifestyle changes before any adverse events occur. In order to get the most accurate results, fasting for a minimum of eight hours — preferentially 12 hours — is recommended. While total cholesterol and HDL (good cholesterol) can be fairly accurately determined in a non-fasting sample, getting the values for triglycerides and LDL (bad cholesterol) requires fasting. And because treatment regimens are determined for the most part by risk factors in conjunction with the LDL level, an accurate reading of this component is critical.

Are you doing everything you can to manage your heart condition? Find out with our interactive checkup.

Drinking water before your cholesterol test will not affect the results, but whether coffee significantly affects cholesterol testing has been debated for years. A 2005 study in The Annals of Pharmacotherapy looked at the effect on cholesterol test results of a single six-ounce cup of coffee without sugar or cream, drunk one hour before testing. The good news is that the study found very small, clinically insignificant changes.

The message then is that it is probably acceptable to have that single cup of black coffee, but if the results are borderline, I would consider repeating the test without the coffee. It may be prudent just to skip the cup for one day and not have the debate!

Fasting for a Blood Test

Why do I need to fast before my blood test?

If your health care provider has told you to fast before a blood test, it means you should not eat or drink anything, except water, for several hours before your test. When you eat and drink normally, those foods and beverages are absorbed into your bloodstream. That could affect the results of certain types of blood tests.

What types of blood tests require fasting?

The most common types of tests that require fasting include:

  • Glucose tests, which measure blood sugar. One type of glucose test is called a glucose tolerance test. For this test you will need to fast for 8 hours before test. When you arrive at the lab or health care facility, you will:
    • Have your blood tested
    • Drink a special liquid containing glucose
    • Have your blood re-tested one hour later, two hours later and possibly three hours later

Glucose tests are used to diagnose diabetes.

  • Lipid tests, which measure triglycerides, a type of fat found in the bloodstream, and cholesterol, waxy, fat-like substance found in your blood and every cell of your body. High levels of triglycerides and/or a type of cholesterol, called LDL can put you at risk for heart disease.

How long do I have to fast before the test?

You usually need to fast for 8–12 hours before a test. Most tests that require fasting are scheduled for early in the morning. That way, most of your fasting time will be overnight.

Can I drink anything besides water during a fast?

No. Juice, coffee, soda, and other beverages can get in your bloodstream and affect your results. In addition, you should not:

  • Chew gum
  • Smoke
  • Exercise

These activities can also affect your results.

But you can drink water. It’s actually good to drink water before a blood test. It helps keep more fluid in your veins, which can make it easier to draw blood.

Can I continue taking medicine during a fast?

Ask your health care provider. Most of the time it’s OK to take your usual medicines, but you may need to avoid certain medicines, especially if they need to be taken with food.

What if I make a mistake and have something to eat or drink besides water during my fast?

Tell your health care provider before your test. He or she can reschedule the test for another time when you are able to complete your fast.

When can I eat and drink normally again?

As soon as your test is over. You may want to bring a snack with you, so you can eat right away.

Is there anything else I need to know about fasting before a blood test?

Be sure to talk to your health care provider if you have any questions or concerns about fasting.

You should talk to your provider before taking any lab test. Most tests don’t require fasting or other special preparations. For others, you may need to avoid certain foods, medicines, or activities. Taking the right steps before testing helps ensure your results will be accurate.

The do’s and don’ts of fasting before routine bloodwork

If you have ever visited a primary care provider, then you have likely been asked to fast before getting routine bloodwork. To learn more, we asked an expert about what you can and cannot do while fasting.

“Some of those blood tests, in either screening for chronic conditions or in monitoring of your chronic conditions, may be affected by some of the nutrients that are in food or drink,” said Jason McKnight, MD, MS, family medicine physician at Texas A&M Health Family Care and clinical assistant professor at the Texas A&M College of Medicine.

McKnight also mentioned the food or drinks you consume the day or night before a blood test does not impact your test results, unlike what you eat or drink the morning of your test.

“It’s recommended that you avoid coffee and other liquids during your fast,” McKnight said. “You never know what kind of nutrient value or additives are in those liquids, so it’s best to just stick with sips of water, unless otherwise cleared by your physician or provider.”

On a similar note, he says to avoid vitamins and snacks, but not to stop any prescribed medications, unless otherwise instructed by your provider. If you have any questions about whether you need to fast and for how long, ask your health care provider the day before your bloodwork.

For Vital Record, this is Mary Leigh Meyer.

— Mary Leigh Meyer

I’m supposed to have my cholesterol checked soon. It’s a simple test, but I’m not looking forward to it since it requires fasting overnight. And that means making a special early-morning trip to my doctor’s office.

But new international guidelines say it’s OK — even preferred — to skip the overnight fast.

To learn more about this small but oh-so-useful shift, I talked with cardiologist Dr. Samia Mora. She helped write the new guidelines, which were published this week in the European Heart Journal and summarized in JAMA Internal Medicine. Mora is director of the Center for Lipid Metabolomics at Brigham and Women’s Hospital and associate professor of medicine at Harvard Medical School.


What was the point of fasting before having a cholesterol test?

Not eating for eight to 12 hours before having blood drawn for a cholesterol test was thought to give a more accurate assessment of total cholesterol, harmful LDL cholesterol, protective HDL cholesterol, and triglycerides, a type of fat-carrying particle. We now know better.

One problem with fasting is that we spend most of the day in the nonfasting state, so the way cholesterol tests are currently done doesn’t necessarily give a clear picture of “normal” levels. Another is that fasting is a hassle for everyone concerned — patients, clinicians, and even lab workers.

What’s behind the new recommendation?

This change has been coming for some time. It is driven by data from a dozen-plus studies that include more than 300,000 people whose cholesterol and other lipids were measured when they hadn’t fasted. Their levels predicted cardiovascular risk, as well as, or possibly better than, fasting lipid levels.

Nonfasting levels might be better?

After you eat, your digestive system converts some of the carbohydrates and fats into triglycerides. Their level in the bloodstream rises, then gradually falls. If the triglyceride level rises too much, it’s a signal that the body has trouble metabolizing food. Think of eating as a stress test for metabolism. That’s something you can’t see if you’ve been fasting.

What does this shift mean?

Everyone wins with this change. People don’t like to fast overnight. Some find it difficult to do, others are even harmed by it, such as those who faint from fasting and people with diabetes who take medications to lower blood sugar. The new recommendation means you can have your blood drawn when it’s most convenient for you, rather than early in the day.

It may even mean one-stop shopping — you can have your blood drawn and then see your doctor, all in the same visit. It’s easier for clinicians, who don’t have to keep track of patients’ special lab visits. Eliminating the fasting requirement will benefit labs, too, since they won’t have to deal with the daily crush of patients first thing in the morning needing blood draws for cholesterol checks.

Does what you eat before the test matter?

Consuming a double cheeseburger, fries, and a milk shake right before having your blood drawn for a cholesterol test may lead to a follow-up fasting test if the triglycerides are very high. But eating normally has little effect on your lipid levels, including triglycerides.

Will this recommendation catch on in the United States?

Health care providers often do what they are used to doing, so it may take a while for some to change to nonfasting cholesterol tests. But we also need to realize that there are advantages to this evidence-based change. Switching to nonfasting cholesterol testing is actually the path of least resistance for patients and clinicians. It also provides a more accurate lipid profile for individual patients.

I believe that getting the word out to clinicians, lab directors, and patients will be enough to make the switch to nonfasting cholesterol tests in a fairly short time.


What to know about fasting before your lab test

With certain blood tests, you may be instructed to fast for up to eight hours before your appointment. Fasting before a blood draw means you don’t eat or drink anything except water.
Don’t wait until the day of your blood draw to ask if you should fast. That could cause your appointment to be rescheduled. If at any point you’re unsure if fasting is required, contact your doctor.

Why do I have to fast before certain lab tests?

Nutrients and ingredients in the food and beverages you consume are absorbed into your bloodstream and could impact factors measured by certain tests. Fasting improves the accuracy of those tests.

Why is water okay to drink while I’m fasting?

Water hydrates your veins. Hydrated veins are easier to find. And that means easier to draw from. Drink plenty of water before having any blood test.

How long do I have to fast for a blood test?

It depends on the test. Fasting for a lab test typically lasts eight hours. Your doctor should give you any special instructions related to your tests, including fasting requirements. Always follow her or his instructions.

Glucose testing that checks blood-sugar levels and tests that determine your cholesterol, triglycerides, and high-density lipoprotein (HDL) levels usually require fasting. Other lab tests may require fasting, which is why you should ask your doctor. If you think fasting might be a problem, schedule your appointment for the early morning and bring a snack for after the appointment.

Can I eat before other types of blood tests?

If it’s a test that does not require fasting then, yes, please eat something before having your blood drawn.

Can I continue taking medications before a blood test?

Unless your doctor says otherwise, take your usual medications. If you’re taking vitamin/mineral supplements, ask whether you should continue those as well.

How soon can I eat after a blood test?

Once you’ve had your blood drawn, you can eat and drink something immediately. It’s a good idea to bring a snack to your appointment. You can also schedule your blood test for the early morning, to minimize the length of time you’ll go without food.

Where do I get my blood drawn?

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What Tests Do I Fast For?

Blood tests help doctors check for certain health problems and find out how well your body is working. Doctors also use them to figure out how well treatments are working. You don’t need to fast before all blood tests. Your doctor will tell you if you need to.

These tests typically require fasting:

  • Fasting blood glucose measures the amount of glucose (sugar) in your blood to test for diabetes or prediabetes.
    Typical fasting time: At least 8 hours
  • Lipid profile is used to check the level of cholesterol and other blood fats. High levels put you at risk for developing heart disease or having a stroke.
    Typical fasting time: 9-12 hours
  • Basic or comprehensive metabolic panel is often part of a routine physical. The tests check your blood sugar, electrolyte and fluid balance, and kidney function. The comprehensive test checks your liver function, too.
    Typical fasting time: 10-12 hours
  • Renal function panel is used to gauge the health of your kidneys and how well they’re working.
    Typical fasting time: 8-12 hours
  • Vitamin B12 test measures how much of the vitamin is in your blood. It can help diagnosis a specific type of anemia and other problems. Some medications can interfere with this test. Tell your doctor about all the drugs you take.
    Typical fasting time: 6-8 hours
  • Iron tests are used to see if iron levels in your system are too low or too high.
    Typical fasting time: 12 hours
  • Gamma-glutamyl transferase (GGT) shows the level of the GGT enzyme in your system. A high reading may indicate liver disease, bile duct problems, or alcohol abuse.
    Your doctor may ask you to fast for at least 8 hours beforehand. You also may need to avoid alcohol and some prescription drugs the day before the test because they can affect GGT levels. Talk to your doctor before stopping any prescribed medicines.

Can you drink coffee before a blood test?

TL;DR while experts have varying opinions on whether you can drink coffee before a blood test or not, the rule of thumb is to know what kind of fast you’ll need to do. Some allow coffee (and even eating), while others will be better off without both. The best way to know is to ask the medical professional prior to the test to eliminate any doubts!

You’re a coffee lover. Coffee’s part of your morning routine.

But what if you have to take a blood test first thing in the morning? Can you still have your caffeine fix?

This seems to be the million dollar question for many. So today, we’re embarking on a mission to find out what the real deal is.

Why fast before blood tests?

WebMD answers the question about why one needs to fast:

Nutrients in food and drinks go into your bloodstream and can change things measured by the tests, skewing your results. For instance, if you eat or drink before a fasting blood glucose test, your blood sugar probably will be higher than if you hadn’t had anything. When you’re fasting, doctors get a baseline result so tests can be compared to give a true picture of your sugar levels over time.

Can you drink water before a blood test?

Registered nurse Kathy Reutter writing at One Medical, says many people mistakenly think they need to avoid water during fasts. Not so, she says. In fact, drinking enough water may help you feel better during a fast and also plump the veins for an easier blood draw by the phlebotomist. She states that blood is about 50 percent water.

Blood work and coffee

But what about coffee? Is drinking it acceptable when fasting?

Doctors keep telling patients that it’s all right to have black coffee before fasting blood work.

However, if you go through various online reports, you’ll note one thing – THEY SAY DIFFERENT THINGS! It seems that jury’s still out on this one.

So here’s the game plan. We’ve taken the liberty to put together what various reports say and we’ll try to come up with a conclusion. Wait ’til you get to the end of this article for the verdict.

  • How about starting off with good news for coffee lovers? According to William Kormos, M.D., the Editor in Chief of Harvard Men’s Health Watch, it’s okay to drink water, plain coffee, or black tea.
  • A 2005 study in The Annals of Pharmacotherapy found that one 6-oz cup of black coffee consumed an hour before the test led to very little (“clinically insignificant”) changes. However, if results turned out to be borderline, it may be worth retaking the test sans coffee.
  • If you forget and have some coffee with cream and sugar or even a meal the morning of a cholesterol test, don’t panic just yet. CBS News reports that when researchers examined data from 209,000 participants in one study with fasting times ranging from one to 16 hours, there were small differences.
  • This article on Livestrong seems to contradict everything else about a fasting blood test:

“While you may consider black coffee little more than water, drinking it causes you to absorb caffeine and other organic compounds into your bloodstream. You need only plain water, without added vitamins, flavoring or carbonation, to achieve the correct fluid and electrolyte balance in your blood chemistry.”

According to Livestrong, “a fasting glucose test measures the level of glucose in the blood during a fasted state,” so you need to avoid food and beverage intake for at least 8 hours.

Here’s Why It’s Important to Fast Before a Blood Test

Before certain types of blood tests, doctors tell patients to fast — to avoid eating or drinking anything for 8 to 12 hours before the test. You also shouldn’t do anything that requires too much exertion, smoke, or even chew gum. It’s okay to take prescription medication, but not over-the-counter stuff. But if you’re starving and desperate for a caffeine fix, isn’t it okay to just have a little nosh and a couple sips of coffee?

19 Foods and Drinks That Are Putting Your Blood Pressure Through the Roof

Nope. When the doctor says to fast, they mean it. Here’s why.

The types of blood tests you need to fast for are typically ones that test for glucose in your blood, cholesterol level, kidney function, electrolyte and fluid balance, vitamin B12, iron, and an enzyme called GGT. Fasting creates a baseline that can be compared against previous or future tests, and eating sends nutrients into your bloodstream that can temporarily change the amount of the specific things the doctor is testing for. So, for example, if you eat something sweet right before a blood test, the amount of glucose in your blood will be higher than if you hadn’t eaten.

So unless you want your blood test results to be skewed, take the doctor’s advice and don’t eat or drink beforehand. And be sure to tell your doctor if you notice any of these signs of an unhealthy heart.

© iStockPhoto

Many types of blood tests require fasting beforehand.

Before certain types of blood tests, doctors tell patients to fast — to avoid eating or drinking anything for 8 to 12 hours before the test. You also shouldn’t do anything that requires too much exertion, smoke, or even chew gum.

It’s okay to take prescription medication, but not over-the-counter stuff. But if you’re starving and desperate for a caffeine fix, isn’t it okay to just have a little nosh and a couple sips of coffee?

Nope. When the doctor says to fast, they mean it. Here’s why.

The types of blood tests you need to fast for are typically ones that test for glucose in your blood, cholesterol level, kidney function, electrolyte and fluid balance, vitamin B12, iron, and an enzyme called GGT.

Fasting creates a baseline that can be compared against previous or future tests, and eating sends nutrients into your bloodstream that can temporarily change the amount of the specific things the doctor is testing for.

Also watch: A blood test could help diagnose depression in the future (Provided by Newsy)

So, for example, if you eat something sweet right before a blood test, the amount of glucose in your blood will be higher than if you hadn’t eaten.

So unless you want your blood test results to be skewed, take the doctor’s advice and don’t eat or drink beforehand. And be sure to tell your doctor if you notice any of these signs of an unhealthy heart.

Also see: How to eat according to your blood type (Provided by Espresso)

Also watch: New blood test for brain injuries approved in U.S. (Provided by CBC)

Click to expand New blood test for brain injuries approved in U.S.CBC

Should You Fast Before a Cholesterol Test?

Your blood will likely be checked using a test called a total lipid profile. To understand your cholesterol test results, you’ll need to know the different types of cholesterol that the test measures and what’s considered normal, potentially risky, and high.

Here’s a breakdown of each type. Keep in mind that people who have conditions such as diabetes may need to aim for even lower numbers.

Total cholesterol

Your total cholesterol number is the overall amount of cholesterol found in your blood.

  • Acceptable: Below 200 mg/dL (milligrams per deciliter)
  • Borderline: 200 to 239 mg/dL
  • High: 240 mg/dL or higher

Low-density lipoprotein (LDL)

LDL is the cholesterol that blocks your blood vessels and increases your risk of heart disease.

  • Acceptable: Below 70 if coronary artery disease is present
  • Below 100 mg/dL if at risk for coronary artery disease or have a history of diabetes
  • Borderline: 130 to 159 mg/dL
  • High: 160 mg/dL or higher
  • Very high: 190 mg/dL and above

High-density lipoprotein (HDL)

HDL is also called good cholesterol and helps protect you from heart disease. This type removes excess cholesterol from your blood, helping to prevent buildup. The higher your HDL levels are, the better.

  • Acceptable: 40 mg/dL or higher for men and 50 mg/dL or higher for women
  • Low: 39 mg/dL or lower for men and 49 mg/dL or lower for women
  • Ideal: 60 mg/dL or higher


High triglyceride levels coupled with high levels of LDL raise your risk for heart disease.

  • Acceptable: 149 mg/dL or lower
  • Borderline: 150 to 199 mg/dL
  • High: 200 mg/dL or higher
  • Very high: 500 mg/dL and higher

You want your cholesterol test results to fall within the acceptable ranges. If your numbers are in the borderline or high levels, you’ll need to make some lifestyle changes and may need to take medication such as a statin. Your doctor may also want to check your levels more often.

Fasting before a cholesterol test

Ask the doctor

Published: August, 2016

Image: jarun011/Thinkstock

Q. Do I still need to fast before getting a cholesterol test? I heard that doing so may not be necessary.

A. For decades, we’ve told people not to eat or drink (except for water) for eight to 12 hours before a cholesterol test. This was based on the belief that fasting provides a more accurate assessment of all the lipids (fats) in the blood, which include cholesterol and triglycerides, a type of fat-carrying particle. But recent studies show that the differences between fasting and nonfasting values for cholesterol are usually negligible.

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We’re supposed to fast for eight to 12 hours before having our blood tested for cholesterol, but wouldn’t it be great if we didn’t have to forgo breakfast and that first cup of coffee?

Well, maybe we can. A new study suggests that most of us can skip fasting and still get accurate cholesterol measurements.

The study, published Monday in the Archives of Internal Medicine, says fasting before the test has little impact on the results. Lipid, or fat, levels in the blood varied very little between those who fasted and those who didn’t, said Canadian researchers who looked at 2011 cholesterol test results for more than 209,000 men and women.

The findings, wrote the researchers, “suggest that fasting for routine lipid level determination is largely unnecessary.” (If you’re having a fasting blood glucose test done at the same time, however, you will need to avoid eating for at least eight hours.)

Participants in the study fasted for anywhere from one to 16 hours beforehand, but cholesterol levels remained fairly steady regardless of fasting time. On average, there was a less than two percent variation in total cholesterol and HDL (sometimes called the “good” cholesterol), and less than a 10 percent variation for LDL (or “bad”) cholesterol across the range of fasting times, reported CBS News.

Only triglyceride levels, another type of blood fat, seemed more affected by fasting. Those who ate an hour before a cholesterol test had triglyceride levels that were up to 20 percent higher than those who had fasted for several hours.

“An awful lot of people probably don’t need to worry about fasting before getting cholesterol screening,” J. Michael Gaziano, M.D., a preventive cardiologist at Brigham and Women’s Hospital who wrote an editorial that accompanied the study, told the Boston Globe.

Researchers wrote that fasting for routine blood work like this is an inconvenience for patients and may discourage some from even having the test. Plus, it’s particularly difficult for diabetic patients who have difficulty controlling blood sugar during prolonged fasting.

While some patients with high triglyceride levels may still require fasting cholesterol tests, others should check with their doctor about whether they really need to skip breakfast before having that blood test.

In other health news:

Many older hospital patients given too much Tylenol. Reuters reports on a new study from two Boston hospitals that finds that one in every 15 patients treated with acetaminophen, or Tylenol, got more than the maximum daily recommended dose at least once. More than 20 percent of those age 65 and older, and close to that many patients with liver disease, were given over 3 grams in a day — above the maximum limit set by the government for both those groups of patients.

Senior calendar girls get naked for a good cause. Sixteen women, all in their 70s and 80s, decided to raise money to help residents of their Maryland retirement community who have been hit hard by rising health care costs. Their idea: Tastefully pose nearly naked for a calendar selling for $15, the Huffington Post reports. The women say they got the idea from Helen Mirren’s 2003 movie “Calendar Girls.” The calendar, called “Going Bare For Benevolent Care 2013,” is being sold on Amazon.

Photo: Neeta Lind via flickr

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