Glucose challenge and glucose tolerance tests are done during pregnancy to test for gestational diabetes, a blood sugar problem that some women get while they are pregnant. The tests are often done together, but sometimes only the glucose challenge is necessary. Health care professionals usually recommend the test between the 24th and 28th weeks of pregnancy.
The glucose challenge test
The glucose challenge test is done first. This one-hour test involves drinking a sweet fluid, waiting an hour, and having blood glucose tested. If the test results are abnormal and show high blood sugar, a glucose tolerance test will be done. That takes about three hours.
The glucose tolerance test
The glucose tolerance test is done if the woman’s one-hour glucose challenge test shows high blood glucose levels.
Most glucose tolerance tests follow these general steps:
- You may be asked to only drink water on the day the glucose tolerance test is given, and it’s possible there will be food and drink restrictions the night before the test.
- A health care provider will take a fasting blood sample from your arm right after you arrive at the hospital or doctor’s office.
- You will be asked to drink a special glucose solution.
- Blood will be drawn several times over the course of several hours to measure the glucose levels in your body.