Heartburn During Pregnancy

Your Guide to a Healthy Pregnancy

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, which contains 50g 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 is processed by your body.

Normal blood glucose levels peak 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 130 mg/dl, you will have another diabetes screening test that requires you to fast before the test.  During the 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 earlier.