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Truth or Myth: Will Tea Affect a Fasting Blood Test?

If you have ever had to fast for a blood test, your doctor will have probably given you the OK for water, tea, and similar beverages. But, how is this possible – will tea affect a fasting blood test in some way?

Well, tea actually doesn’t have an impact on your fasting blood test, so it is fine for you to drink. If you are curious to find out why this is, though, read on…

Why Can You Drink Tea While Fasting?

So, why are you given a free pass on tea and water but have to stay away from food? Well, this all depends on what your doctor is actually testing for.

The most common tests that require fasting are glucose and triglyceride tests. Here, doctors need to check the levels of blood glucose or fatty particles in the blood. As such, they need to make sure that sugars or fats in your meals won’t interfere with the readings.

Tea, however, doesn’t contain these ingredients. As such, it won’t have any kind of impact on the test. This is why you are free to have your daily cup. However, your doctor will probably advise you to skip the milk and sugar if you usually add it to your tea.  

Of course, it is a good idea to clarify with your doctor just how much tea you can drink. They may also advise you to drink green tea instead of black tea if they are looking for something specific in your tests.

Extracting blood from Syringe

Can You Drink Tea Before Any Fasting Blood Test?

As mentioned above, the kind of fasting that you need to do will depend on the kind of test that you are taking. Due to this, your doctor may ask you to drink nothing but water until the test has been completed. In these cases, you will have to give your tea a miss.

See, tea contains caffeine and the caffeine can skew certain test results. This means that your doctor won’t be able to get an accurate idea of what is actually going on. If you do slip up and accidentally have some tea despite your doctor’s instructions, let them know. You may have to postpone or reschedule the test.

If you have been warned off any kind of drink, it is a good idea to skip the herbal teas as well. It is difficult to know the exact effect that these teas can have on your system. So, it is better to steer clear until the test is over.

Can You Drink Anything Before a Fasting Blood Test?

Even if your doctor tells you that water, tea, and coffee are fine, this doesn’t automatically mean that all beverages are on the table. You are still going to need to avoid sodas, carbonated drinks, energy drinks, sugary drinks, and fruit juices as well.

All such drinks contain sugars, additives, and more. Due to this, they may skew the results in a variety of ways. Thus, you should stay away. If you have any confusion it is a good idea to clarify with your doctor to preserve the accuracy of the tests.

So, there you have it – in most cases, tea won’t have an impact on your fasting blood test. In some instances, though, you may need to stop or reduce your consumption until the test has been completed. More often than not, this will depend on the kind of test you will be undergoing.

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An Important Disclaimer: The information on this site is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment.
Author Bio
Dr. Dheena Sadik
Dr. Dheena Sadik is a consultant Nutritionist and Dietician. She has over a decade of experience in the health and fitness industry. However, her love for tea began long before she understood the health benefits of tea. Growing up in Sri Lanka, Dheena had the privilege of being surrounded by the world-famous Ceylon tea. This is what got her started on her exploration of the various types of tea. She has now extensively tasted and examined teas from all over the world.
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