A GCT is frequently performed as a routine screen for GDM in all pregnancies at 24 to 28 weeks of gestation. It should be performed earlier if symptoms are present.
Some sources recommend screening at the first prenatal visit if there are risk factors.
Repeat at 24 to 28 weeks if previous test is negative. A blood glucose level is obtained 1 hour after a 50 g oral glucose load. Follow-up an abnormal GCT result. The patient must eat a diet containing at least 150 g of carbohydrate for 2 days. The patient has a serum glucose level obtained after an overnight fast and then ingests 100 g of glucose solution.