The glucose challenge test is used to screen for gestational diabetes. The test is generally done between weeks 24 and 28 of pregnancy.
However, it can be done as early as your first prenatal visit if you're at high risk of gestational diabetes due to obesity, a personal history of gestational diabetes, a family history of diabetes or other factors. Abnormal test results early in pregnancy might indicate that you have pre-existing type 2 diabetes that wasn't previously recognized — not gestational diabetes.
Most women who have gestational diabetes deliver healthy babies. However, without careful management, gestational diabetes can lead to various pregnancy complications, such as excess fetal growth — which might increase the risk of birth injuries or prompt a C-section delivery.
You can eat and drink normally before the glucose challenge test.
The glucose challenge test is done in two steps. When you arrive at your health care provider's office or lab, you'll drink about 5 ounces (about 148 milliliters) of a syrupy glucose solution that contains 1.8 ounces (50 grams) of sugar.
You'll need to remain in your health care provider's office or lab while you wait for your blood sugar level to be tested. Consider bringing a quiet activity with you.
One hour later, a blood sample will be taken from a vein in your arm. This blood sample will be used to measure your blood sugar level.
After the glucose challenge test, you can return to your usual activities immediately.
Results of the glucose challenge test are given in milligrams per deciliter (mg/dL) or millimoles per liter (mmol/L).
- A blood sugar level below 140 mg/dL (7.8 mmol/L) is considered normal.
- A blood sugar level of 140 mg/dL (7.8 mmol/L) or higher might indicate gestational diabetes.
Some clinics or labs use a lower threshold of 130 mg/dL (7.2 mmol/L) when screening for gestational diabetes.
If the results of your glucose challenge test indicate the possibility of gestational diabetes, your health care provider will do another test — typically the glucose tolerance test — to determine the diagnosis.