Fasting for a Blood Test

Some examples of common blood tests that usually require fasting are:

• Blood glucose, also called blood sugar, tests. These tests measure the level of blood glucose in a sample of your blood. They are used to help diagnose and monitor diabetes, prediabetes, and gestational diabetes (diabetes that starts during pregnancy). Not all blood glucose tests require fasting, so ask your provider if you need to fast for your test.
• Cholesterol levels tests (lipid panel). These tests measure the level of fats, called lipids, in your bloodstream, including cholesterol and triglycerides. The test results help show your risk of getting heart disease and can be used to monitor your health after a cardiac event like a heart attack or stroke.
• Basic metabolic panel (BMP). This is a group of tests that measures several natural chemicals in your blood. The results give your provider information about how well your organs are working, including your heart, kidneys, and liver.

In some cases, you may also be asked to fast for:

• Liver function tests. This group of tests measures several proteins and other substances related to your liver function. Test results can give your provider information on your liver’s health.
• Renal function panel. This is a group of tests that measure several waste products and substances related to your kidney function. The results are often used to monitor your kidney function if your provider suspects kidney disease or if you have diabetes.

Whether or not your provider asks you to fast for these tests depends on several factors. For example, some liver function tests only require fasting if they’re ordered as part of a comprehensive metabolic panel.

Other types of tests not listed here may require fasting. Therefore, you should always ask your provider if you aren’t sure whether you should fast before your test.