Diagnosing gestational diabetes is a two-step process.Diagnosing gestational diabetes is a two-step process.
Step 1: The Glucose Challenge You drink a concentrated glucose beverage, then wait an hour for a blood test. If your one-hour blood-sugar level is more than 140 milligrams of glucose per deciliter of plasma (mg/dL) but less than 200 mg/dL, you'll be referred to Step 2 for a more definitive diagnosis. If it exceeds 200, you'll be diagnosed with GDM and won't need further testing.
Step 2: The Glucose-Tolerance Test You fast overnight and arrive at the lab in the morning for a blood sample to measure your fasting blood-glucose level. Then you drink a concentrated glucose solution and wait around as your blood is tested every hour for the next three hours. If two readings are abnormal, you'll be diagnosed with GDM. This chart shows the levels that the American Diabetes Association considers abnormal at each interval of the test:
Interval Abnormal reading Fasting 95 mg/dL or higher One hour 180 mg/dL or higher Two hours 155 mg/dL or higher Three hours 140 mg/dL or higher