Reference Values During Pregnancy

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3 hour Oral Glucose Tolerance Test, OGTT, GTT (serum, plasma)

   Units Fasting 1 hour 2 hour 3 hour
mg/dL 95 180 155  140
mmol/L  5.3 10  8.6 7.8

The 3 hour OGTT is a diagnostic test for gestational diabetes. It measures glucose concentrations over three hours  after a 100-g oral glucose load. The test is done in the morning after an overnight fast of between 8 and 14 hours, and after at least 3 days of unrestricted diet (≥150 g carbohydrate per day) and physical activity.

At least two or more values must be equaled or exceeded for a positive diagnosis.

These values represent the equivalent glucose oxidase plasma values calculated from the original data using the Somogyi-Nelson technique [3-5].


1.  *Guidelines for Care, California Diabetes and Pregnancy Program,2002
2. American Diabetes Association.Diagnosis and classification of diabetes mellitus. Diabetes Care. 2009 Jan;32 Suppl 1:S62-7 PMID:19118289
3. O’Sullivan JB, Mahan CM. Criteria for the oral glucose tolerance test in pregnancy. Diabetes 13:278-85, 1964 PMID: 14166677
4. Carpenter MW, Coustan DR: Criteria for screening tests for gestational diabetes. Am J Obstet Gynecol 144:768-73, 1982.PMID: 7148898
5. Sacks DA, Abu-Fadil S, Greenspoon JS, Fotheringham N: Do the current standards for glucose tolerance testing represent a valid conversion of O’Sullivan’s original criteria? Am J Obstet Gynecol 161:638-41, 1989. PMID: 2782345

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