Gestational Glucose Tolerance Diagnostic Test (Three-hour, ACOG Recommendations)

Diagnose gestational diabetes.

In 2013,² the American College of Obstetricians and Gynecologists (ACOG) recommended that all pregnant women be screened for gestational diabetes mellitus (GDM)—whether by patient history, clinical risk factors, or with a 50-gram, one-hour loading test at 24 to 28 weeks of gestation to determine blood glucose levels—and suggested relying on the result of the 100-gram, three-hour oral glucose tolerance test for diagnosis (often referred to as a "two-step" method).

The American Diabetes Association (ADA)¹ released standards that vary from the ACOG recommendations. The ADA standards recommend a simplified "one-step" approach to the screen and diagnosis of gestational diabetes mellitus with a 75-gram, two-hour glucose tolerance test.

The LabCorp test according to the ADA recommendations is Gestational Glucose Tolerance Screening and Diagnostics Test (Two-hour, ADA Recommendations) [101000].

1. American Diabetes Association. Standards of Medical Care in Diabetes—2015: Summary of revisions. Diabetes Care. 2015 Jan; 38(Suppl 1):S4. PubMed 25537706

2. American College of Obstetricians and Gynecologists. Committee on Practice Bulletins—Obstetrics. Practice Bulletin N° 137: Gestational diabetes mellitus. Obstet Gynecol. 2013 Aug; 122(2 Pt 1):406-416. PubMed 23969827

3. LabCorp internal studies.

For three days prior to the test, patients should eat an unrestricted diet of 150 or more grams of carbohydrate and be permitted unrestricted physical activity. Patients should be instructed to eat and drink nothing except water for at least eight hours and not more than 14 hours before the test. Patients should also be advised to discontinue, whenever possible, all nonessential medication that can affect glucose metabolism at least three days before testing.