oral glucose tolerance test

OGTT

A screening test for diabetes mellitus (DM), in which plasma glucose levels are measured after the patient consumes an oral glucose load. In screening patients for type 2 DM, measuring fasting plasma glucose levels or checking a hemoglobin A1c level is generally preferable to an OGTT because the former tests are simpler, cheaper, and better tolerated by patients. An OGTT reveals type 2 DM when plasma glucose levels exceed 200 mg/dl 2 hr after drinking a 75-g glucose load. Plasma glucose levels between 140 mg/dl and 199 mg/dl suggest impaired glucose tolerance.

Gestational Diabetes Mellitus

In pregnancy, a modified OGTT is used to screen women with risk factors for gestational diabetes (GDM), including obesity, family history of type 2 DM, age greater than 25 years, and a history of unexplained stillbirths. At 24 to 28 weeks' gestation, a 50-g glucose load is given; 1-hr plasma glucose levels greater than 140 mg/dl constitute a positive screening result. Any patient having a positive test result should then undergo a 2-hr, 100-g OGTT to determine whether GDM is present. See: table

Screen high-risk women at first visit, and screen all women at 24–28 weeks' gestation with 75g oral glucose tolerance test. American Diabetes Association revised Standards of Medical Care, published in Diabetes Care special supplement, January 2011. International Association of Diabetes and Pregnancy Study Groups published in Leary, J. et al. (2010). Best Practice Research Clinical Endocrinology and Metabolism 24 (4), 673.

Time:	Glucose level exceeds:
Fasting	92 mg/dl
60 min	180 mg/dl
120 min	155 mg/dl
180 min	140 mg/dl