The Oral Glucose Tolerance Test (OGTT) is a test that measures how well the body uses sugar (glucose) and is used to screen for gestational diabetes, a type of diabetes that develops during pregnancy. The test involves drinking a sweet liquid containing glucose and getting blood drawn at specific intervals. The glucose tolerance test can be used to screen for type 2 diabetes as well. The test is usually performed between 24 and 28 weeks of pregnancy, but it may be done earlier if the woman has a high risk for diabetes. There are two types of glucose tests that a pregnancy care provider may offer: a glucose challenge test and a glucose tolerance test. The glucose challenge test is a screening test that detects an increased probability of gestational diabetes, while the glucose tolerance test is used to diagnose gestational diabetes. If a woman fails the glucose challenge test, she may be asked to take the glucose tolerance test. If the blood glucose level is higher than 140 mg/dL (7.8 mmol/L) after the one-hour test, the doctor will recommend the three-hour test. If the blood glucose level is higher than 190 mg/dL (10.6 mmol/L) after the one-hour test, the woman will be diagnosed with gestational diabetes. If two or more of the results are higher than normal, the woman will be diagnosed with gestational diabetes. If diagnosed with gestational diabetes, the woman may need to make modifications to her diet and use a blood glucose meter to measure her blood sugar at specific times during the day. If diet changes alone don’t help, she may need insulin to manage gestational diabetes.