Glucose Test During Pregnancy

It’s very important to diagnose gestational diabetes early and set up a treatment plan with your care team to manage the condition. This can help you avoid issues such as:

• High blood pressure, or preeclampsia, during pregnancy, which can decrease blood flow to the placenta
• Premature birth
• Cesarean birth, due to a larger baby
• Increased risk of developing type 2 diabetes or hypertension later in life

Because gestational diabetes can cause many issues later in pregnancy, it’s important to work with your provider to diagnose the condition early and manage it through healthy eating habits, glucose monitoring and medication. You might even be referred to a high-risk specialist, like the ones in our Maternal Fetal Medicine Program, to monitor the rest of your pregnancy.

Although blood sugar typically returns to normal after the birth, gestational diabetes can have lingering effects, such as a higher risk for diabetes for both you and your child as you and your baby get older.

Risks of a glucose test

The glucose challenge test is a safe, routine and noninvasive screening with no risk to you or your baby.

What happens during a glucose test?

This is a simple, routine test. Consider wearing loose sleeves for the blood draw and bring a snack for after the appointment. Typically, the test will follow these steps:

• First, you’ll drink a sugary liquid from your provider.
• Don’t eat or drink anything else (including chewing gum) for an hour.
• Then, we’ll draw your blood to check your sugar level.

If your sugar level is too high, you may be asked to complete the three-hour glucose tolerance test to confirm whether you have gestational diabetes.

Results of a glucose challenge test

Results from the blood test should be available within a few days. Results are measured in milligrams per deciliter (mg/dL) of blood. Your provider will review your blood sugar levels and explain what they mean for your pregnancy.

This screening test identifies who may be at risk but does not diagnose gestational diabetes on its own. Results may look like this:

• Normal: Less than 135 mg/dL
• Borderline or elevated: 135-179 mg/dL. Your provider will recommend a follow-up, three-hour glucose tolerance test for confirmation.
• High: 180 mg/dL or higher. Your provider may diagnose you with gestational diabetes without the need for further testing or may talk to you about the three-hour glucose test.

Three-hour glucose tolerance test

This three-hour test is the follow-up diagnostic test if the first screening results are elevated. This test measures how your body processes glucose over time. Steps for this test include:

• You’ll need to fast overnight to test your fasting blood sugar.
• You’ll drink another glucose solution.
• You’ll have your blood drawn at one-hour intervals for three hours.

Your provider will compare your results to standard values to determine whether you have gestational diabetes.

What happens if my glucose test results are high?

One abnormal result typically is not enough to diagnose gestational diabetes. If your blood sugar level is high on any two or more values of the three-hour test, you’ll be diagnosed with gestational diabetes.

It’s important to remember the condition is very manageable, and the management starts with changes to your diet and physical activity. Your provider may recommend medication if needed. You will need to monitor your blood sugar levels at home for the duration of your pregnancy.

Specialists in our Maternal Fetal Medicine Program are uniquely trained to help you manage gestational diabetes, to ensure that your baby arrives safely and you remain healthy throughout the rest of your pregnancy.

How do I prepare for a glucose test?

Preparing for your glucose test is simple, and your care team will give you clear instructions in advance.

For the one-hour glucose challenge test (screening):

• No fasting is required. You can eat and drink as you normally would before your appointment, but try to avoid anything extremely sugary right before your test because it may affect your results.
• Wear a short-sleeved or loose-fitting shirt for easy access to your arm.
• Bring a light snack for after the test if you tend to feel faint or lightheaded after blood draws.

For the three-hour glucose tolerance test (diagnostic):

• Fasting is required. You’ll need to avoid eating or drinking (other than water) for eight to 12 hours before your test.
• You may want to schedule the test early in the morning so you can fast overnight.
• You’ll have your blood drawn four times – before drinking the glucose solution, and then one, two, and three hours afterward.
• Bring something to read or listen to, as you’ll be seated comfortably for about three hours.

Consider arranging a ride home afterward, especially if fasting or multiple blood draws make you feel tired or dizzy. Your care team will review your results and next steps after the test.