Can I Take Pre-workout Before Blood Test? (Explained)

Regular blood testing is one of the most important ways to monitor your overall health. However, there are certain substances that you should avoid eating or drinking before taking a blood test becasue they can interfere with your result.

In general, you cannot take a pre-workout before the fasted blood test. Most pre-workout supplements contain caffeine, which is a diuretic that removes water from your body and can affect your lab results. However, certain types of blood tests don’t need to be done on an empty stomach.

There you have my overall answer but if you wanna know more about why you should avoid pre-workouts before blood work or which types of blood tests are ok to eat and drink, keep reading.

Can you take a pre-workout before blood work?

I’m doing a blood test and I need to know if I can drink pre-workout prior to my test? The answer to this question will depend on the type of blood test you’re doing.

Most of the blood tests that measure blood glucose, cholesterol (lipid panel), or metabolic panel do require you to drink only water and abstain from any other beverages for up to 12 hours before the test.

This means you should avoid taking any pre-workout supplements before blood work becasue they can mess up your results. Some of the ingredients in pre-workouts like creatine can elevate your fasting plasma glucose levels, without even secreting insulin.

Kieron B. Rooney, Ph.D., a biochemist and associate professor from the University of Sydney said that creatine supplementation may result in abnormalities in glucose homeostasis in the absence of changes in insulin secretion.

This means that creatine does not increase insulin levels, however, it does change glucose levels.

In his recent article, Dr. Rooney clarifies that “increasing glucose levels before taking a blood glucose test is not recommended”.

What about pre-workouts without creatine?

I understand that not all of the pre-workouts contain creatine, however, most of them do include caffeine, which is also a potent stimulant and diuretic.

Caffeine blocks the adenosine receptors, which are strictly related to the homeostasis of salt and water, which leads to caffeine-induced diuresis (basically you pee more and more often).

Also, keep in mind that pre-workout contains almost 3x more caffeine than a standard cup of coffee.

Drinking large amounts of caffeine before the test can lead to changes in blood water concentrations and mild dehydration.

Obviously, that can greatly alter the results, especially if you’re doing a coagulation blood test or if you’re measuring renal function, liver function, or sodium and potassium levels. On the other hand, if you’re doing blood work for c-reactive protein or drug tests, it’s not that important.

Can I take a Non-Stim pre-workout before a blood test?

Okay, first of all, non-stim pre-workouts are basically pre-workout supplements that don’t have caffeine in them. However, they still have several other compounds that can alter the blood test results, like beta-alanine.

Beta-alanine enhances carnosine biosynthesis, which plays a role in metabolism.

You should not take non-stim pre-workout before a fasted blood test becasue they contain beta-alanine. Beta-alanine enhances carnosine biosynthesis and can lower fasting glucose levels, according to studies.

No joke.

Joseph J Matthews, Ph.D., from Birmingham City University said that beta-alanine and carnosine supplementation decreases fasting glucose levels, as well as fasting insulin levels.

According to Dr. Matthews, treatment with beta-alanine and carnosine increases the glucose uptake in skeletal muscle cells in both diabetic and nondiabetic adults, which lowers overall glucose levels in the blood.

Which blood tests are OK for pre-workout?

The good news is that not all require you to come on an empty stomach. However, it is better to be safe than sorry so I recommend you should ask your doctor or call the lab in advance (I’m not a medical doctor so I cannot give you medical advice).

Here is the list of the blood tests where you can drink pre-workout prior.

  • Thyroid panel blood test – A thyroid blood test checks how is your thyroid, and how well it is reacting to certain hormones.
  • Enzymes blood tests – Enzymes blood tests check your levels of creatine kinase, creatine kinase-MB, and Troponin.
  • Sexually transmitted infections blood test – This test is looking for things like chlamydia, gonorrhea, herpes, and other STDs.

Okay, let’s wrap this up.

So, should you take a pre-workout before a blood test?

At the end of the day, whether you should or not take a pre-workout before a blood test will depend on the type of the test, and (most importantly) how important are the results for you.

Personally, I would not take anything apart from the water before my blood work if the test is something really important to me.

Some jobs and professions do require a mandatory medical examination, including a fasted blood test, to issue a medical certificate.

If you’re a seafarer, police officer, military personnel, fireman personnel, or even a driver (applies to some countries), you won’t be able to work without a valid medical certificate.

Also, if you like to travel a lot to foreign countries like Canada, Australia, or South Africa, some visa applications also require a medical examination that includes basic blood work.

They usually check for leprosy, tuberculosis, syphilis, or gonorrhea.

On the other hand, if your blood test is not that important, and you accidentally drink pre-workout before, nothing bad is gonna happen.

Just be sure to contact the laboratory and they may ask you to have the blood drawn all over again.

Here you can learn if taking supplements before an exam helps with studying.


Taking pre-workout before a blood test can mess up your results in a variety of ways, depending on the ingredients in the supplement. Caffeine has a dehydrating effect on the body, whereas creatine can increase glucose levels.

Certain types of blood tests will require you to abstain from anything but water for up to 12 hours prior to the test to ensure that your test results are accurate.

However, other types of blood tests do not require you to come on an empty stomach.

Michal Sieroslawski

Michal is a personal trainer and writer at Millennial Hawk. He holds a MSc in Sports and Exercise Science from the University of Central Lancashire. He is an exercise physiologist who enjoys learning about the latest trends in exercise and sports nutrition. Besides his passion for health and fitness, he loves cycling, exploring new hiking trails, and coaching youth soccer teams on weekends.

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