Laboratory Testing
Dieting and Weight Loss

Can you drink black coffee before a blood test that requires fasting?


Wiki User

Users have said:

No seems to be the answer. My solution to this is to drink hot water from my coffee mug. It really helps your craving for coffee and hydrates you as well.
  • No. The most common blood tests done that require fasting are lipids (cholesterol, LDL, HDL and Triglycerides) and fasting blood sugar (note, glycohemoglobin does not require fasting). Of these, the blood sugar and triglycerides are the most variable. They are affected mostly by sugar intake. It is very important to stay hydrated before a fasting blood test so that your blood and urine do not falsely indicate your kidneys are malfunctioning. Although water is best, caffeine has not significantly affected the blood tests of my patient population.
  • Depends on the test, and if it's a fasting test, but Generally speaking no, caffeine affects liver function and releases hormones from your adrenal glands, even decaf has caffeine in it.
  • No, if you ingest anything other than water the results will be inaccurate. Some people believe that black coffee will not have an affect on glucose, however the caffeine alone has an impact on the pancreas which in turn effects insulin, which effects glucose.
  • I am going for a blood test tomorrow morning (consisting of a whole range of sub-tests including cholesterol, thyroid, etc.). My instructions were 12 hours of fasting including all solids and liquids BESIDES water as well as black coffee in the YES you may have BLACK coffee. Cream and sugar obviously affect results.
  • No, just clear liquids. Hit up the tea if your desperate for caffeine
  • Generally, no. You should try to drink only water.
  • It depends on the test your having done. If you drink black coffee, with no additives, you can still have fasting labs done. However, coffee will increase your blood pressure and affect some tests .... especially a CRP.
  • Your paying for these tests. I would recommend no coffee 10-12 hours prior if your not sure. The best method is to call the laboratory.
  • It is best if you were not to have anything to eat or drink before having bloodwork done or any test as such because the coffee might change the result of the test in some way, maybe water is fine though.
  • Yes. You are only supposed to drink water.