Glucose Test Pregnancy: Steps, Results & What to Expect

A glucose test during pregnancy is used to help identify gestational diabetes. It is usually done between 24 and 28 weeks of pregnancy, even when there are no signs or symptoms of diabetes.

Symptoms of diabetes can include excessive hunger or frequent urination. However, gestational diabetes can also occur without noticeable symptoms.

Screening usually starts with a 50 g, 1-hour glucose challenge test. If the result is higher than expected, a 100 g, 3-hour oral glucose tolerance test may be done to confirm the diagnosis.

How the test is done

Gestational diabetes screening is usually performed between 24 and 28 weeks of pregnancy using a two-step approach.

According to the American College of Obstetricians and Gynecologists (ACOG), this two-step approach typically starts with a 50 g, 1-hour glucose challenge test and is followed by a 100 g, 3-hour oral glucose tolerance test if the first result is abnormal.

First, a glucose challenge test (GCT) is performed:

• No fasting is required

• The pregnant person drinks a solution containing 50 g of glucose

• A blood sample is collected 1 hour later

If the screening result is higher than expected, an oral glucose tolerance test (OGTT) is recommended to confirm the diagnosis. This test involves the following steps:

• The pregnant person fasts for at least 8 hours

• A fasting blood sample is collected

• The pregnant person drink a solution containing 100 g of glucose

• Blood samples are collected 1, 2, and 3 hours after drinking the solution

After the test, the person can return to eating normally and wait for the results.

If the results are abnormal, the OB-GYN or midwife may refer the pregnant person to a registered dietitian to start an appropriate meal plan.

Regular follow-up is also important to help prevent complications for both the pregnant person and the fetus.

Glucose test results

ACOG commonly recommends a two-step approach to screen for and diagnose gestational diabetes. This usually starts with a 50 g, 1-hour glucose challenge test.

If the result is abnormal, a 100 g, 3-hour glucose test is done to confirm the diagnosis:

Gestational diabetes is diagnosed when two or more values are at or above the cut-off points.

Besides routine screening between 24 and 28 weeks of pregnancy, people with risk factors may also be tested earlier for preexisting diabetes.

According to the American Diabetes Association, preexisting diabetes may be suspected when fasting blood glucose is 126 mg/dL or higher, random blood glucose is 200 mg/dL or higher, or glycated hemoglobin (HbA1c) is 6.5% or higher. If any of these results are abnormal, the doctor may order further tests to confirm the diagnosis.

Monitoring blood glucose levels during pregnancy is important to help prevent complications for both mother and baby. It also helps guide the best treatment plan, including personalized dietary changes with support from a registered dietitian.