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Confirmatory Test for Gestational Diabetes:
The 3 hour Oral Glucose Tolerance Test

  • Values > 140 mg/dl and <180 on the 1 hour oral glucose tolerance test require follow-up with a 3-hour 100 gram oral glucose tolerance test (OGTT)
  • If the patient has a screening value > 180 mg/dl, a fasting blood sugar should be checked. An elevated fasting value of > 95 and screening test > 180 mg/dl provides two abnormal values, and treatment for gestational diabetes is recommended.

    3-hour 100 Gram Oral Glucose Tolerance Test (OGTT)
    The 3 hour OGTT is done after an overnight fast for at least 8 hours but not more than 14 hours after at least three days of unrestricted diet and physical activity.

      Abnormal 3-hour 100 gram OGTT values are:

    • Fasting > 95 mg/dl
    • One hour> 180 mg/dl
    • Two hour > 155 mg/dl
    • Three hour > 140 mg/dl

      At least two out of four values must be equaled or exceeded to diagnose gestational diabetes.

      If only one value is elevated then

    • Manage with diet and exercise.
    • Consider retesting at 32 to 34 weeks for patients with risk factors.


        *Guidelines for Care, California Diabetes and Pregnancy Program,2002

  • Created: 12/18/2002
    Update: 11/2/2004

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