Why do I need a glucose tolerance test?

The oral glucose tolerance test (OGTT) is done to:

Check pregnant women for gestational diabetes. You have an increased chance of developing gestational diabetes if you:

• Have had gestational diabetes during a previous pregnancy.
• Have previously given birth to a baby who weighed more than 9 lb (4.1 kg).
• Are younger than age 25 and were overweight before getting pregnant.
• Diagnose prediabetes and diabetes.