Glucose Tests During Pregnancy: What to Expect

Also called the gestational diabetes test, glucose screening is crucial to detecting this often-symptomless pregnancy complication. Learn what these tests are and why they're important.

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Glucose screening and glucose tolerance testing during pregnancy can help detect gestational diabetes. Catching it early gives you a chance to minimize the risks associated with the condition.

Gestational diabetes is a condition in which your body has too much sugar (called glucose) in the blood. Seven out of every 100 pregnant people will develop it, according to March of Dimes, and this can lead to problems—for both the expectant parent and baby. Gestational diabetes can cause problems with fetal growth, as well as increase the risk for C-section and high-risk conditions like preeclampsia.

Find out everything you need to know about glucose screening tests, from what they are to when they're administered.

What Is a Pregnancy Glucose Screening Test?

A pregnancy glucose tolerance test, or glucose screening test, is a test that measures how your body responds to glucose. Specifically, it measures your blood after you ingest a sugary drink to see how much glucose is in your blood.

The test is usually done between 24 and 28 weeks of pregnancy. This is not a fasting test. You'll be given a 50-gram glucose solution that must be consumed within five minutes; it tastes a bit like syrupy flat soda. An hour after you've finished drinking the beverage, a blood sample is taken from a vein in your arm, and the glucose level is analyzed.

If the test result is abnormal, you'll be given an additional confirmatory test called the three-hour glucose test. Unlike the first glucose tolerance test, which is for screening purposes, the three-hour test is a diagnostic tool for gestational diabetes.

Do You Have to Take a Glucose Screening Test While Pregnant?

The U.S. Preventive Services Task Force and American College of Obstetricians and Gynecologists (ACOG) recommend all pregnant people be screened for gestational diabetes with a glucose test. It's more important now than ever before, given the increasing numbers of pregnant people affected by obesity and a sedentary lifestyle.

Detection and treatment of gestational diabetes can reduce the risk of pregnancy complications like preeclampsia, an overly large baby, high blood pressure, and C-section. "Studies show a significant reduction in serious complications with treatment of gestational diabetes," reiterates American Family Physician in a review of ACOG guidelines.

Early gestational diabetes screening is recommended for people with certain risk factors, including a history of gestational diabetes, obesity, and known impairment to glucose metabolism, according to American Family Physician.

How Can You Prepare for a Glucose Screening Test?

Before your one-hour pregnancy glucose test, it's recommended to follow a diet that's high in carbohydrates for three days, so your pancreas gets accustomed to processing simple sugars. Your health care provider can give you more information on what to eat prior to testing.

Note that some people find the syrupy glucose solution unpleasant or even nausea-inducing. You can increase your odds of successfully completing the test by drinking it cold, sipping slowly over five minutes, or using an anti-nausea medication beforehand. If you still have trouble tolerating it, your OB-GYN can discuss alternatives, such as checking blood sugars for a week using a glucometer.

Are There Any Risks Associated with Pregnancy Glucose Tests?

While the glucose test itself does not come with any real risk, there are certain risk factors for developing gestational diabetes—including being over the age of 25, having a family history of diabetes, or having obesity. That said, half of those who develop gestational diabetes have no known risk factors, making testing so important.

What Happens If Your Glucose Screening Test Is Abnormal?

If your pregnancy glucose test is elevated or "abnormal," your body may not be producing enough insulin. Results over 130 mg/dL could be indicative of a problem. However, before your doctor can diagnose you with gestational diabetes, you will need to take a confirmatory three-hour glucose test.

To prepare for this three-hour gestational diabetes test, you will need to fast overnight and then drink a solution with an even higher dose of glucose. Your blood will then be sampled several times over a period of about three hours and tested for abnormal levels of glucose.

How Can You Lower Your Glucose Levels?

If you've been diagnosed with gestational diabetes, don't fret. Many people with this condition have healthy pregnancies and healthy babies. That being said, here are some ways to control your blood sugar levels during pregnancy.

Dietary Changes

Eating a healthy, well-balanced diet is important for all pregnant people, but it is particularly important for those with gestational diabetes. Certain foods should be avoided or restricted, including simple and refined carbohydrates. Ask your health care provider for more information.


Exercise, or moderate physical activity, is a great way to combat gestational diabetes, as it "helps their [pregnant peoples] bodies' insulin work better, which is an effective way to control blood sugar," a guide from the U.S. Department of Health and Human Services explains. However, you should consult with your doctor before starting a new workout routine.


"Even if you do everything your health care provider tells you to manage your gestational diabetes, you still might need to take insulin during your pregnancy to keep it under control," the U.S. Department of Health and Human Services writes. "[This] does not mean that you didn't try hard enough or that you failed at taking care of yourself." Indeed, fasting blood sugars can be especially hard to control despite dietary and lifestyle changes, as they reflect the influence of the pregnancy on your pancreas. It's important to see medication as another management tool if it becomes necessary.

The good news? Gestational diabetes responds well to healthy lifestyle changes and medication treatment, so you can keep yourself and your baby healthy.

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