What to Expect With Glucose Tests During Pregnancy

For most people, glucose tests are a normal part of prenatal care. Glucose screening and glucose tolerance testing during pregnancy can help detect gestational diabetes, a type of diabetes that only happens during pregnancy. Identifying the condition as soon as possible can help minimize the risks associated with gestational diabetes for both you and your baby.

Gestational diabetes is a condition that causes glucose (sugar) to build up in your body, leading to high sugar levels. Gestational diabetes occurs when your body isn't able to use insulin, the hormone responsible for breaking down glucose, effectively. John Hopkins University explains that gestational diabetes is often different than "regular" diabetes, because it's pregnancy hormones that make the insulin not as effective, which is why gestational diabetes disappears after pregnancy.

Six out of every 100 pregnant people will develop gestational diabetes, according to March of Dimes and it can lead to complications such as your baby being larger-than-average, having difficulty managing their own blood sugar and temperatures. If you have gestational diabetes, it even increases your baby's risk for type 2 diabetes later in life. Gestational diabetes can also increase the risk for C-sections and high-risk conditions like preeclampsia.

Fortunately, gestational diabetes is manageable and the glucose test during pregnancy will help your doctor identify if you have this common condition. Find out everything you need to know about glucose tests during pregnancy, from what they are to when they're administered.

What Is a Glucose Test During Pregnancy?

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

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 your body is producing and/or using insulin effectively, your glucose levels will be in the normal range. But if they are too high, it's an indication that you either have insulin resistance (when your cells aren't able to use insulin well) or aren't making enough insulin to properly break down glucose. Either way, abnormally high glucose levels indicate that you could be at risk for gestational diabetes.

If the first glucose 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 Test While Pregnant?

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant people be screened for gestational diabetes with a glucose test. All pregnant people should be screened for gestational diabetes between 24 and 28 weeks of pregnancy, but if you have certain risk factors for gestational diabetes, your doctor may recommend earlier screening as well.

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. It is important to note that while gestational diabetes is a condition that occurs only during pregnancy, some pregnant people may have gone into pregnancy with a mild form of type 2 diabetes that was undetected.

That means that while many people may not have any blood sugar issues after pregnancy, some will need to continue blood sugar management once the baby is born as well. Additionally, the ACOG notes that having gestational diabetes does raise your and your baby's risk of developing type 2 diabetes later in life.

How Can You Prepare for a Glucose Test During Pregnancy?

For your initial one-hour glucose testing, no special preparation or fasting is needed. Your doctor will give you more information about how to prepare, but in general, you don't have to do anything special: just go to the laboratory, drink the glucose solution, wait exactly one hour, then return to have your blood drawn.

If you need the three-hour glucose test, however, you will be asked to fast for 8 hours before getting your blood drawn. Then, the lab will give you a glucose liquid to drink and you will have your blood taken again at 1, 2, and 3 hours after drinking the glucose solution.

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?

There are no risks associated with getting the pregnancy glucose test for you or your baby. However, skipping the test could put you at risk of going through pregnancy with undetected gestational diabetes, which could lead to health risks and complications for you and/or your baby. If you have any concerns about the glucose test or questions about what it involves, be sure to talk to your doctor. Remember, your doctor wants you to have a healthy pregnancy that is as stress-free as possible, so don't hesitate to ask any questions you might have.

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 or is not able to use the insulin it is making. The American Diabetes Association (ADA) notes that a blood glucose level of over 140 mg/dL could be indicative of a problem.

However, your doctor won't diagnose you with gestational diabetes until you have had a three-hour glucose test as well. With the three-hour glucose test, your blood will be drawn at 1, 2, and 3 hours after drinking the glucose solution and while you are fasting.

If you have two or more of the following results, you will be diagnosed with gestational diabetes:

• First hour: a blood glucose level over 180 mg/dL,
• Second hour: a blood glucose level over 155 mg/dL
• Third hour: a blood glucose level of more than 140 mg/dL

How Can You Lower Your Glucose Levels During Pregnancy?

Gestational diabetes can be effectively managed and many people with this condition have healthy pregnancies and healthy babies. Your doctor will discuss the ways you can help control your blood sugar levels during pregnancy, which may include:

Dietary changes

Eating a 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 healthcare provider for more information.

Exercise

The ACOG recommends physical activity was a way to manage gestational diabetes during pregnancy. According to the ACOG, you should always talk to your doctor about what physical activity might be right for you during your pregnancy, but in general, walking at least 30 minutes per day for at least 5 days a week is a great place to start. Additionally, a brisk 10-15 minute walk after eating can help balance your blood sugar levels.

Medication

In some cases, even if you follow all of your doctor's recommended strategies for gestational diabetes, the pregnancy hormones your body produces will make your cells too insulin-resistant to manage your blood sugar on your own. In that case, your doctor may recommend that you take insulin to help manage your blood sugar levels, says the ACOG. Insulin doesn't mean you've done anything "wrong." Instead, it's just another tool to help you have the healthiest pregnancy you can.