Glucose Test: Gestational Diabetes Screening
The glucose test screens for gestational diabetes — a form of diabetes that develops during pregnancy. It's done routinely at 24–28 weeks and involves drinking a glucose solution and having blood drawn.
Typically performed: Weeks 24–28
The 1-Hour Glucose Challenge Test (GCT)
The initial screening test. You drink 50g of glucose solution (Glucola) and have blood drawn one hour later. No fasting is required. A blood glucose above the threshold (typically 130–140 mg/dL, varies by lab) means you'll need the 3-hour diagnostic test. About 15–23% of people fail the 1-hour test, and of those, only 1 in 3 will be diagnosed with gestational diabetes.
The 3-Hour Glucose Tolerance Test (GTT)
If you fail the 1-hour test, the diagnostic 3-hour test is next. You fast overnight, then have a fasting blood draw, drink 100g of glucose solution, and have blood drawn at 1, 2, and 3 hours. Failing 2 or more values results in a gestational diabetes diagnosis.
Managing Gestational Diabetes
Gestational diabetes is managed through dietary changes (limiting refined carbohydrates, increasing protein and fiber), blood sugar monitoring, and sometimes insulin or oral medication. With proper management, outcomes for baby and mother are generally very good. It does increase risk of large baby, C-section, and preeclampsia.
Frequently Asked Questions
Usually no fasting is required for the 1-hour screening test. However, some providers recommend avoiding high-sugar foods beforehand. Confirm with your provider's office.
You'll work with your healthcare team on a management plan — most commonly dietary changes and blood sugar monitoring. About 15–20% of people with GD need medication (insulin or metformin).
In most cases, yes — blood sugar levels return to normal after delivery. However, gestational diabetes significantly increases lifetime risk of type 2 diabetes. A follow-up glucose test at 6–12 weeks postpartum and ongoing screening is recommended.