The Glucose Tolerance Test or GTT helps to detect the body's response to sugar. This test is used as a screening tool to check for Type-2 diabetes as well. This test is required for diagnosis of impaired fasting glucose and impaired glucose tolerance. It is recommended for all pregnant women to check for gestational diabetes mellitus using a 50-g dose at 24 to 28 weeks of pregnancy; if that is abnormal, OGTT should be performed for confirmation and is gold standard for diagnosis of gestational diabetes mellitus.
This test is done by taking a blood sample from the person's arm for testing. If you are a pregnant woman getting yourself tested for diabetes, you may be asked to fast for 8 hours and then to drink about 100 grams of sugar. The blood sugar levels are checked in 3 hours. If type-2 diabetes is being checked, the person is made to drink 75 grams of sugar and blood sugar levels are checked after 2 hours.