Are you a coffee lover looking to take a blood test? Is avoiding coffee for more than a few hours is a difficult task for you? Well, when it comes to a blood test, you have to be sincere else you risk skewing the final results.
Can you drink coffee before a blood test? No, it is advisable to not drink any coffee (even black coffee) before taking a blood test. This must be followed for all blood tests that require you to fast for 8 to 12 hours. Even if the blood test doesn’t require fasting, we’d recommend taking your last coffee at least 2 to 3 hours before your blood test. This way, it won’t distort your final results.
Should You Take Coffee Before a Blood Test?
The easiest answer to this question is No.
It is always better to be safe than be sorry.
When you’re blood test requires you to fast for around 8 to 12 hours, it is very important to avoid coffee consumption during that time frame.
If you’re not taking a fasting blood test, like blood sugar level, then there is a little play area that might allow you to drink coffee. Even then, when you’re taking serious tests like the Cholesterol test, you might not want to drink any coffee and risk affecting your final results.
If you absolutely must consume caffeinated coffee, then you can have it black without any sugar or cream. If you’re someone who only takes coffee with cream or milk, then this isn’t an option for you. Even this is only allowed for non-fasting blood work. Drinking any coffee or beverage is strictly a no when it comes to taking a fasting blood sample.
Why do we have to be this strict with coffee? I mean, isn’t it just a harmless drink? Well, coffee can affect your blood test results in a number of ways. Let’s take a look at them.
How Does Coffee Affect Blood Tests?
It contains caffeine and Plant matter
If you consume black coffee, it will affect blood test results because it contains plant matter and a high dose of caffeine.
This is especially true if you take ground coffee which has a high degree of cholesterol (think French Press). These minerals are known to distort the results of blood tests.
Coffee is also a diuretic
Another possible reason why coffee affects blood tests is that it is a diuretic. Taking diuretic beverages will cause you to urinate often which will, in turn, lead to water loss and dehydration.
One of the effects of dehydration is that it complicates the testing process as it will be difficult for the expert to find a vein in your arm to draw out blood. Invisible veins will make the proceeds complicated and time-consuming.
What about decaf coffee? Is decaf coffee a diuretic? We have discussed this subject in pretty good detail. Just follow the link.
So, in a nutshell, while consuming coffee will not put you at any risk, it may complicate the proceeds and the eventual result of the test.
Fasting Blood Panels vs. Non-Fasting Blood Panels
Blood tests are conducted to perform certain checks. So each check has unique criteria depending on the test.
For the purpose of this article, let’s break down the tests into two broad groups. Let’s discuss them below.
Fasting Blood Panels
Fasting blood panels usually is done to measure the glucose level in the blood. Oftentimes, this test is done to check for prediabetes or diabetes symptoms.
Before you come for this test, the doctor will ask you to stay away from food or liquid for about 8-12 hours so as to get a high degree of accuracy.
So consuming coffee within this timeframe will distort the results. There are different things this panel checks for, and we document them below.
BMP: This is the Basic Metabolic Panel which checks the effect of diabetes on the kidney. This test requires fasting on your path.
Glucose: For a blood glucose test, the doctor wants to see your sugar level. For accuracy, this test requires a fasting period of 12 hours at least. So avoiding coffee is a must.
Comprehensive Metabolic Panels: This test looks at different elements in your blood like protein, electrolytes, kidney and liver functions, and the general functions of your body. A comprehensive metabolic panel test is more comprehensive.
Gamma Glutamyl Transferase: Also called GGT, this test checks the number of enzymes in your body. Doctors recommend it to check the number of enzymes in your body.
Patients, to take this test, need to avoid alcohol for at least 24 hours before the test and food 8 hours before the test.
Lipid profile: This one is to check the cholesterol level and requires fasting as well, so no food or liquid should be taken at least 8 hours before the test, including alcohol.
Nutritional tests: Then there are other nutritional tests to check for minerals and vitamins in the body. Most of the tests under this category require 8-12 hours of fasting.
Note: There above is by no means exhaustive as there are many other tests under this category.
Non-Fasting Blood Panels
The second category is the non-fasting blood panel. This one is basically meant to check for triglycerides. Triglycerides can be measured in your blood steam whether you rest or not, so taking coffee before this test will not affect the outcome. Common examples of Non-fasting blood panels tests include.
Antinuclear Antibody: Also called ANA, this own tests for Lupus and general autoimmune diseases. It does not require fasting
Amylase: This is a test for pancreatic cancer and related diseases.
A1C: Is for treating prediabetes and diabetes in patients and can be done over an extended period of as long as three months.
Electrolyte: An electrolyte test checks for the balance of electrolytes in the blood.
HIV antibody: This one checks for HIV and AIDS.
Others include
- Activated Partial Thromboplastin
- Mono
- Lyme disease
So from the above, you can see that most Fasting blood panels tests require you to fast before you submit yourself for the test, while non-fasting tests do not require fasting. Taking coffee before you a fasting blood panels test will affect the results the same as if you consume water or any other food or drink.
However, if you take water, coffee, or food by accident after your doctor has advised you not to, it will be in your best interest to let your health provider know that you have broken the fasting window. If you hide this information, the result of your test may come out as false since the medical expert will misinterpret the results.
The best thing to do is to let them know the truth and ask for the test to be rescheduled for another time. While this will delay it by a few days, you will at least be sure of getting accurate results after the test. It will also save money by avoiding repeated tests.
Let’s wrap this quick.
Submitting yourself for a blood test is not a big deal if you choose not to make it one.
You can do simple things to prepare yourself before D-day, like following the doctor’s instructions and staying away from coffee.
Can I take a cup of coffee before a blood test?
Like we’ve said a couple of times in this post, not drinking coffee is better for most blood tests. But if you must drink coffee and if you’re going to take a non-fasting blood test, then a cup of coffee won’t hurt.