A glucose challenge test is a blood test used to screen women for diabetes during pregnancy. The test evaluates the body’s ability to metabolize glucose (blood sugar).  

The test is usually ordered between the 24th and 28th weeks of pregnancy, sometimes earlier. Blood is drawn one hour after the patient drinks a sugary solution. Results are compared to normal values.

Abnormal results may indicate gestational diabetes. However, not all women with abnormal test results have diabetes. To diagnose gestational diabetes, a physician will order an additional glucose test.

The terms “glucose challenge test” and “oral glucose tolerance test” (OGTT) are sometimes used interchangeably. However, the OGTT is a more involved blood test that can be used in diagnosing type 2 diabetes and prediabetes in addition to gestational diabetes.