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Doctor visits and tests during pregnancy are essential to make sure that your baby is developing and that you are healthy. One essential test is the glucose challenge, which happens early in the third trimester. This test checks for abnormal blood sugar levels, indicating gestational diabetes.

You may have heard about a nasty glucose drink or scary-sounding three-hour tests. Learn what to expect from the third-trimester glucose test and your pregnancy glucose test results.

What Is the Glucose Test During Pregnancy?

All pregnant women have a routine glucose screening blood test between weeks 24 and 28 of pregnancy. A pregnancy glucose test measures how much sugar (glucose) is in your blood an hour or more after drinking a measured amount.

Glucose tests during pregnancy are a version of the fasting blood glucose test. This test tells doctors if your blood sugar levels are too high. Too-high blood sugar signals gestational diabetes, which develops only during pregnancy.

During pregnancy, hormones created by the placenta change how the body makes and uses insulin. Insulin is a hormone that helps regulate how much sugar is in your blood after you eat.

This sugar is an essential energy source for your body’s cells, but when levels are too high, it can hurt your baby. Gestational diabetes increases your risk of:

• Having a too-large baby (nine pounds or more), which makes delivery much harder and increases the chance that you’ll need a C-section.
• Sudden high blood pressure called preeclampsia, which can develop later in pregnancy.
• An early delivery, before your baby’s lungs fully develop.
• Health problems in your baby like low blood sugar, jaundice, or diabetes.
• A late miscarriage or a stillborn baby.

All pregnant people can develop gestational diabetes. You might have a higher risk if you:

• Are overweight.
• Have prediabetes or polycystic ovary syndrome.
• Gain too much weight during your pregnancy.
• Had gestational diabetes with a previous pregnancy.
• Have a family history of diabetes.
• Are African American, American Indian, Asian American, Hispanic/Latina, or Pacific Islander American.

If gestational diabetes causes symptoms, they are mild. They’re often mistaken as typical pregnancy symptoms — being thirstier than usual or peeing a lot. You may not feel as hungry, especially in the mornings, or feel unwell after eating too many carbohydrates. It’s easy to miss this health condition, so it’s crucial to have this test.

What Happens During a Pregnancy Glucose Test

There are two different types of pregnancy glucose tests. Your doctor will decide which is best for you, depending on your health and gestational diabetes risks. They might also recommend doing the test earlier than 24 weeks if you’re at higher risk for gestational diabetes.

One-hour glucose challenge test

You don’t have to do anything to prepare for this test, and you can eat and drink as you usually would. Sometimes doctors suggest taking the test early and avoiding carbohydrates during breakfast.

You’ll drink a few ounces of a very sweet glucose beverage after arriving for the test. It’s essential to drink it within 15 minutes. The health professional administering the test will watch you drink it and ensure you finish it on time.

Then, you’ll wait an hour in the waiting room or your car before a tech draws your blood. They’ll test the blood to see how much glucose is present. Normal blood glucose is less than 135 mg/dL.

You may need a follow-up three-hour oral glucose tolerance test if yours exceeds that.

Oral glucose tolerance test (3-hour test)

The 3-hour test is done fasting, so you should not eat or drink anything except water for at least eight hours before. Try to schedule the test first thing in the morning and take at least half a day off work for it. You’ll likely feel pretty bad after only having a glass of sugar water all morning.

When you arrive, a health care professional will draw your blood. Then, you’ll drink the sweet glucose beverage. The tech will draw your blood again two or three more times over three hours.

Those blood glucose readings will tell your doctor how well your insulin works and whether it can regulate your blood sugar. If two or more of those results come back high, you may have gestational diabetes.

If Pregnancy Glucose Levels Are High

Finding out you have a health condition is scary, especially when pregnant. But you and your health care team can manage gestational diabetes. Your doctor might recommend:

• Keep a log of your food intake and blood sugar values and review them with your doctor and dietitian.
• Eat a carbohydrate-controlled diet. A registered dietitian can teach you how to plan healthy meals and count carbohydrates.
• Get regular, moderate exercise. This helps you keep your weight gain within healthy limits and can help your body process carbohydrates better.
• If these interventions do not help regulate your blood sugars, doctors may prescribe insulin.

During labor, your doctor will test your blood glucose and give you any needed insulin shots. They’ll also need to test the baby’s blood sugar once they’re born with a heel stick test.

Gestational diabetes usually goes away after your baby is born. Several weeks after you deliver, your doctor may do another test to make sure your blood sugar is back to normal.

Gestational diabetes usually goes away after pregnancy, but it signals an increased risk of diabetes later in life. It’s vital to stay in contact with your health care team even after your diabetes resolves. You can take steps now to stay healthy and avoid diabetes later.