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Can You Have Coffee Prior To Blood Test – Yes Or No, Know Here

You need to have a blood test today, and you’re hoping that drinking coffee will improve your performance. Can you drink coffee before a blood test?

Many people have asked themselves whether or not it is OK to have coffee before a blood test. 

This article will be beneficial for you if you drink coffee all the time and have to get your caffeine fix before a blood test.

Let’s get started!

Is it OK to have coffee before the blood test?

The short answer is yes, but the dosage will depend on the substance being tested for and your tolerance.

How long before a blood test can you drink coffee?
The validity of this statement depends on whom you ask. Some doctors say that black coffee is fine to drink before a cholesterol test.

There’s no harm in including it in your morning routine if you feel you need your caffeine pick-me-up as long as you don’t add cream or sugar.

An online coffee resource says that it is best to avoid coffee before a blood test because caffeine could interfere with the results.

So, which is the correct answer? The truth may have its roots in what type of test you’re going to take.

These drinks will not affect typical laboratory tests such as cholesterol (lipid panel), metabolic panel, and blood glucose measurement. We will discuss which blood tests might require a complete fast.

Even though coffee is digested more quickly, it can also alter blood parameters. In fact, before a fasting blood test, it is recommended not to drink coffee.

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How Does Coffee Interfere With Blood Tests?

Different types of medical tests require additional preparation. So, the question we have to answer is what kind of blood test you will be taking?

There are several laboratory tests where drinking coffee before a blood test could interfere with the accuracy.

The most common difficulties that require fasting include A1C, Acne Blood Test, ACTH Stimulation Test, and Thyroid-Stimulating Hormone (TSH) Test.

If you are not sure whether you should drink coffee before a blood test, it is better to ask your doctor or nurse. However, they may not give you a definite answer because each type of blood work must meet different laboratory guidelines.

If you have diabetes, the doctor would ask you about your eating habits and stress levels before a blood test. Also, he will perform a blood test where your blood is drawn after fasting for at least 8-12 hours.

However, if you are taking medication, discuss your health and dietary habits with your doctor.

What happens in the liver? 

If you have diabetes or take medication, you shouldn’t drink coffee before getting a blood test. Caffeine dramatically increases sugar levels in the blood by blocking the production of insulin – the hormone responsible for controlling sugar levels in the body.

When this happens, the body secretes more insulin, leading to a sensitivity of the beta cells.

If you drink coffee before getting a blood test, your insulin resistance level may go up, making getting accurate blood glucose test results very challenging.

However, if your doctor is going to examine your insulin levels, it is best you fast for 12 hours before the procedure. This means that even decaf coffee is forbidden when taking an insulin blood test because it contains less than 0.3% caffeine, which is the legal limit.

Some medications used for cancer treatment may cause liver damage if you drink coffee before the blood test. You will need to discuss this with your doctor.

What are the effects on cholesterol? 

What should you not do before a blood test?

Caffeine can, directly and indirectly, affect cholesterol monitoring. Instantly, it can inhibit caffeine molecules from excreting into your bile in the small intestine.

This results in a rise in cholesterol levels; however, this will go down again when you take any medicine.

Indirectly, caffeine increases the body’s need for cholesterol. However, it also decreases the absorption of some cholesterol-lowering drugs.

If your doctor wants to test your cholesterol levels before a blood test, it is best not to drink coffee for at least 24 hours.

What are the effects of triglycerides? 

As you already know, drinking coffee can raise your blood sugar and insulin levels. When this happens, triglycerides decrease because the liver starts to digest them faster than it usually does.

However, if you already have high triglycerides, there is a risk of making the situation worse by drinking coffee before a blood test.

What are the effects on uric acid? 

If your doctor wants to test your uric acid levels, that is another good reason to stay away from coffee for at least 24 hours before the blood collection.

Caffeine raises uric acid levels because it causes the liver to metabolize purines (key source for uric acid production) faster.

If your doctor will perform a blood test, it is best not to drink coffee for at least 12 hours before the procedure. This means that decaf coffee is not allowed either; however, tea and herbal teas are fine.

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What if I accidentally eat or drink before my blood test?

Coffee has different effects on different people. For example, if you are susceptible to low blood sugar or other medical conditions, the coffee could affect your results.

Technical errors are also common. For example, if your medicine contains caffeine, you are likely to be affected by any amount of coffee that you consumed the night before the blood test.

Finally, different tests vary in how they measure the blood test samples. For example, when a lab measures the amount of sugar in your blood or cholesterol levels, it does not pick up any metabolites of caffeine that may be present in your body.

This means that if you drink coffee, your blood sugar may be lower than usual, but the lab would not know about it.

However, if a different type of test detects caffeine, your fasting blood sugar or cholesterol levels may be affected. It is why you should always talk to your doctor before blood tests and before getting any medical procedure.


Coffee can help to relieve anxiety before a blood test, particularly if you fear needles. But consuming coffee when fasting can harm your performance. Thus, a ride for more blood extraction if you neglect the instructions from your doctor. 

You should do your research to determine what blood tests are being done and whether you might need to do other tests. Then, in case you need to fast, please do so easily and quickly. 

After the test, you can still go for a rewarding cup of coffee. If you don’t have to fast, drink as much coffee as you want!

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