What does fasting mean?

Your doctor may tell you you need to fast for some of the lab work we perform, but what does that mean?

Fasting means not eating or drinking for a period of time before your lab tests. Some blood tests are sensitive to food and drink in your system, and fasting helps ensure that the test results are more accurate.

Some common tests that require fasting are blood cholesterol, triglyceride and glucose level tests. Some tests that check for vitamin levels, such as Vitamin E or A may also require fasting. Your doctor will let you know whether your test requires it.

How long do I fast?

It depends. Some blood tests need you to fast for at least 12 hours. Some other tests only require an eight-hour fast. Your provider will tell you when to begin your fast, so you can plan your lab visit accordingly.

Many people fast overnight, then have their labs drawn early in the morning. That’s why our lab is so busy in the morning! Just make sure you follow the guidelines your provider gave you so the test results are not tainted.

What can’t I eat or drink?

  • Food
  • Gum, especially gum with sugar
  • Liquids other than water, unless with your doctor’s permission

What can I drink?

Water is allowed during a fast. Black coffee or tea may be allowed, but check with your doctor, because some tests are sensitive to caffeine.