Fasting for Blood Work

Everything we eat and drink has short and/or long term influences on how our bodies function and on our lab test results. Your practitioner may request that you “fast” before your blood is drawn. If your doctor did not tell you how long to fast, you should not eat or drink anything for approximately 12 hours prior to the test.

What is FASTING?
Fasting requires that you do not eat or drink for a specified period of time. Typically, you are allowed to drink only water during the fasting period. This helps you stay hydrated and makes drawing your blood easier. Tea and coffee contain caffeine, which can make your test results inaccurate. For fasting labs, you may also be asked not to chew gum, smoke, or even exercise. Exercise, like digestion, can affect your test results.

Why is FASTING necessary?
Everyday, the normal range for blood sugar and lipids fluctuate hour to hour depending on recent ingestion of food, drink, and exercise. By fasting, your physician can obtain a baseline laboratory test value that is not influenced by these factors.

If you are taking medications, especially medications that require you to eat food while taking a dose, please consult with your physician about what to do during the FASTING preparation.

After your blood is drawn
The fasting period is over and you will want to eat and drink something. It’s a good idea to bring along a healthy snack to eat so you can eat as soon as possible. Try to schedule your blood draw for early in the morning so you don’t have to go too long without eating during the day.