Health guide
Glucose tolerance test in pregnancy: screening for gestational diabetes
Gestational diabetes is high blood sugar that develops during pregnancy, usually with no symptoms. It is screened with a glucose tolerance test (GTT/OGTT), most often between 24 and 28 weeks: you drink a measured glucose solution and your blood sugar is checked at set times. Catching it early lets simple steps protect both mother and baby for the rest of the pregnancy.
Reviewed by Dr. Vishal Singh, Lab Director
Who is screened, and risk factors
- Routine screening for all at 24-28 weeks
- Gestational diabetes in a previous pregnancy
- A family history of diabetes
- Being overweight or having PCOS
- A previous large baby (over 4 kg)
- Excessive thirst or tiredness (often there are no symptoms)
How the test works
You give a fasting sample, drink a glucose solution, and give one or more further samples (commonly at 1 and 2 hours). The pattern shows how well your body is handling sugar during pregnancy. Some clinics use a single 75 g test; follow the exact instructions and timing your doctor gives you.
Why it matters
Untreated gestational diabetes raises the chance of a large baby, delivery complications, and later diabetes for mother and child. The reassuring part: most cases are well controlled with diet and monitoring, and blood sugar usually returns to normal after delivery, with a follow-up test recommended later.
This guide is for general information and is not a diagnosis. Always discuss your symptoms and results with a doctor. LabONE includes a free doctor consultation with every report.
Tests that help
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Frequently asked questions
When is the glucose tolerance test done in pregnancy?
Most commonly between 24 and 28 weeks, and earlier if you have risk factors such as previous gestational diabetes, PCOS, or a strong family history.
Do I need to fast for the pregnancy sugar test?
Usually yes. A fasting sample is taken first, then you drink the glucose solution and give further samples. Follow the exact timing your doctor provides.
Not sure where to start?
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