Can You Drink Tea Before a Fasting Blood Test?

Curated by Claudia Shannon / Research Scientist / ishonest


Tea does break a fast for blood work. Fortunately, these fasts are temporary most last for between 8 and 12 hours, according to the U.S. National Library of Medicine (NLM).

Can You Drink Tea Before a Fasting Blood Test?

For instance, if you're curious if you can drink green tea before a blood test, it's best to abstain green tea contains caffeine, which can affect your blood and hydration levels to potentially alter test results, per the Cleveland Clinic.

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So can you drink herbal tea before a fasting blood test? After all, it doesn't have any caffeine. Alas, the answer is still no even caffeine-free tea could affect a fasting blood test.


Not all blood tests have the same fasting requirements, per the NLM, so follow the instructions provided by your doctor to best prepare for your upcoming blood work.

Making the Fast Bearable

Now you know you can't drink tea before fasting blood work.

But it's still possible to make a fast more manageable: Dana Neutze, MD, PhD, associate medical director of the Family Medicine Center at the University of North Carolina, Chapel Hill, and an assistant professor in the Department of Family Medicine, suggests trying to schedule your blood work for as early in the day as possible.

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"I recommend people come in first thing in the morning so that they don't have to wait too long," she says. And staying well-hydrated may curb creeping hunger pangs, she says.

It may also be helpful to bring a snack with you to eat at your appointment, as it's typically OK to chow down as soon as the blood test is complete, according to the NLM.

And remember, fasting requirements can vary depending on the blood test, so always check with your doctor to make sure you know what to do leading up to your visit.


It's also important to avoid other beverages like juice, coffee, soda, flavored water and carbonated water before a fasting blood test, according to the NLM and Cleveland Clinic.

Common Fasting Blood Tests

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Even though tea does break a fast for blood work, fasting is not necessarily a prerequisite for all blood tests. But two types of blood tests do require fasting to obtain the best results, Dr. Neutze says. According to the NLM, these are:

  • Glucose tests, which measure your blood sugar
  • Lipid tests, which measure your cholesterol and triglyceride levels

It's important to be fasted for a glucose test to ensure it accurately detects if your blood sugar levels are unnaturally high (whereas temporary high blood sugar after a meal is normal), per the Cleveland Clinic. "If [your blood glucose] is high after an eight-hour fast, that's an indication that there is a problem with sugar processing or that you have prediabetes or diabetes," Dr. Neutze says.

Fasting can also be important before certain triglyceride and cholesterol tests for a similar reason. "Triglyceride levels are the component of cholesterol that are most affected by fasting or not fasting," Dr. Neutze says.

Read more on: livestrong

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