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Glucose Tolerance Test


Updated February 15, 2014

Glucose Tolerance Test

The glucose tolerance test is used to diagnose diabetes.

Image: © A.D.A.M

Definition: The glucose tolerance test is a lab testing method that is completed in order to assess how the body metabolizes blood sugar. The oral glucose tolerance test (OGTT) is the most common glucose tolerance test.

Your doctor may order an OGTT if she suspects you are developing diabetes. You will be told not to eat or drink after midnight the night before the OGTT. At the time of testing, your blood will be taken, and then you will drink a liquid containing glucose. Your blood is taken again, and your blood glucose level is tested every 30 to 60 minutes (for up to two to three hours) to assess how the glucose is metabolized.

A blood glucose level of 200 mg/dl or greater is indicative of diabetes.

Also Known As: oral glucose tolerance test

Examples: The glucose tolerance test is a screening tool used to diagnose diabetes.

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