Definition of Glucose test - blood:

A blood glucose test measures the amount of a sugar called glucose in a sample of your blood.

Glucose is a major source of energy for most cells of the body, including those in the brain. Carbohydrates (or carbs) are found in fruit, cereal, bread, pasta, and rice. They are quickly turned into glucose in your body. This raises your blood glucose level.

See also:

• Glucose test - CSF
• Glucose test - urine
• Glucose tolerance test
• Home blood glucose monitoring

How the test is performed:

A blood sample is needed. For information on how this is done, see: Venipuncture.

How to prepare for the test:

The test may be done while you are fasting or at random.

• If you are having a fasting glucose blood test, you should NOT eat or drink for 8 hours before the test.
• A random glucose test can be done at any time of the day, but results depend on what you drink or eat before the test, as well as your activity.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

Your doctor may order this test if you have signs of diabetes. However, other tests (glucose tolerance test and fasting blood glucose test) are better for diagnosing diabetes.

The blood glucose test is also used to monitor patients who have the diabetes. It may also be done if you have:

• A change in behavior
• Fainting spells
• Seizures for the first time