Fasting for a Blood Test Test
Fasting for a blood test means you should not eat or drink anything except plain water for several hours before the test. You should also avoid chewing gum, smoking, and exercising during this time.
What this test measures
Fasting helps ensure that your blood test results are not affected by food, drinks, or activities. Your provider will give you specific instructions to follow.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Frequently asked questions
What does it mean to fast for a blood test?
It means you should not eat or drink anything except plain water for several hours before your test.
Can I drink water while fasting for a blood test?
Yes, you can drink plain water.
Can I chew gum while fasting?
No, you should not chew gum while fasting for a blood test.
Can I smoke while fasting?
No, you should not smoke while fasting for a blood test.
Can I exercise while fasting?
No, you should not exercise while fasting for a blood test.
Related lab tests
Sources
- MedlinePlus: Fasting for a Blood Test — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.