What is an oral glucose tolerance test?
The oral glucose tolerance test is performed to screen for gestational diabetes. This test involves quickly drinking a sweetened liquid (called Glucola), which contains 50 g of glucose. The body absorbs this glucose rapidly, causing blood glucose levels to rise within 30 to 60 minutes. A blood sample is taken from a vein in your arm about 60 minutes after drinking the solution. The blood test measures how the glucose solution was metabolized (processed by the body).
Normal blood glucose levels peak at 160 to 180 mg/dl within 30 to 60 minutes after drinking the glucose solution. A higher than normal blood glucose level does not always mean you have gestational diabetes.
Diagnostic test
If your blood glucose level was greater than 135 mg/dl, you will have another diabetes screening test that requires you to fast (not eat anything) before the test. During this second test, called the 100-gram oral glucose tolerance test, your blood glucose level will be tested four times during a three-hour period. If two out of the four blood tests are abnormal, you will be diagnosed with gestational diabetes.
When is the oral glucose tolerance test performed?
Gestational diabetes is generally diagnosed between the 24th and 28th week of pregnancy when insulin resistance usually begins. If you have had gestational diabetes before, or if your health care provider is concerned about your risk of developing gestational diabetes, the test might be performed before the 13th week of pregnancy.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 10/31/2006
