Pregnancy Tests

Having a normal diet before your glucose test can give you accurate results.
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How To Prep For Your Gestational Diabetes Test

Hint: just eat like you normally do.

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When you're growing another human, taking care of your body is arguably your number one priority. At the beginning of your third trimester, your doctor will order a glucose tolerance screening to test for gestational diabetes. Knowing what to eat before gestational diabetes test can help you feel prepared and make sure you get the most accurate results.

“In the United States, we practice universal screening for gestational diabetes, as identifying and treating gestational diabetes can reduce the risk of pregnancy complications,” Dr. Michael Cackovic, maternal fetal medicine physician at The Ohio State University Wexner Medical Center, tells Romper “Screening is usually performed between 24 and 28 weeks of pregnancy, but may be performed earlier for risk factors such as previous pregnancy with gestational diabetes, obesity, a strong family history of diabetes or polycystic ovarian syndrome.”

Because a test for gestational diabetes is all about measuring your blood sugar, it's important to know what you do and don't need to do to prepare, but there’s a lot of conflicting information online and out in the world about how to do so. One reason for this is that there are different types of gestational diabetes tests that your doctor may order. Depending on which test you take, there are different rules around what you can eat or drink before hand, so it’s important to know which test you’re taking.

Types Of Gestational Diabetes Tests

“There are a few ways to screen for gestational diabetes,” Cackovic tells Romper.

The most common type of screening test involves having your blood drawn one hour after drinking a sugary sweet drink. “You will be given 50 grams of glucose in a specially formulated drink to drink within a few minutes,” Cackovic says. “Your blood will be tested in one hour to measure your blood sugar level. If the level is normal, no other testing is necessary.”

For this specific type of screening test, Cackovic says that “you should eat and drink normally.” No fasting or special diet is necessary.

If your results for this screening are high (“usually 130 to 140 mg/dl,” says Cackovic) a second, longer test called a Glucose Tolerance Test (GTT) will be scheduled by your doctor to determine whether or not you have gestational diabetes. “The test is done by measuring your fasting blood sugar level, then again in one, two, and three hours after you drink a glucose drink that contains 100 grams of glucose (twice the amount in the one-hour test.),” Cackovic says.

For the longer test, again, no specific foods are recommended, but Cackovic notes, “It is important to not limit your diet in the two to three days before the GTT since low food intake may cause the test results to be falsely high.” Gestational diabetes is then diagnosed if two or more of your blood draws show elevated blood sugar levels, though some doctors may diagnose after one elevated result if you have other risk factors.

Alternatively, Cackovic says that your doctor may use a different type of oral GTT in order to test for gestational diabetes. For this type test, you would need to avoid eating prior to the test.

“The test is done by measuring your blood sugar level before you eat anything in the morning — fasting, then again one and two hours after you drink a glucose drink that contains 75 grams of glucose,” Cackovic says. “Gestational diabetes is diagnosed if you have one or more elevated blood sugar values.”

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How To Prepare For Your Gestational Diabetes Screening

Eating normally prior to your screening (or fasting, if you are having the test that requires it) won’t require much prep or planning on your part, but there are some other tips to keep in mind that may help make your experience a bit more pleasant. (I can speak from experience when I say that the longer tests are no walk in the park.)

The sugary drink tastes like really sweet, flat soda and comes in different flavors, and you need to drink the whole thing fairly quickly. Many people say it's better served cold, so it may be helpful to call the lab before you go to see if it's refrigerated. If not, you could bring a cup of ice if you think it'll make it all go down easier.

Certified Nurse Midwife Kathy Loebel tells Romper that patients sitting through the three-hour gestational diabetes test may want to “bring a book or a laptop to occupy your time.” Just make sure that whatever you bring to entertain yourself doesn’t require you to be up and moving. “It is important not to have activities in between your blood draws as this could affect your results,” Loebel says.

“Additionally, I instruct patients to bring with them a small juice pack and a small snack so as soon as that last blood is drawn, they are able to eat something,” Loebel says. This will help prevent you from feeling jittery after downing a sugary drink and sitting still for a while.

While it may seem like an inconvenience to have to take the time to drink an extra sweet drink, hang out in the lab waiting room, and then get a blood test (or two or three), it's pretty wonderful that science can tell us if something in our pregnancy needs attention, so we can give our babies the best chance at being born healthy, and stay healthy ourselves.


Dr. Michael Cackovic, maternal fetal medicine physician at The Ohio State University Wexner Medical Center

Kathy Loebel, MS, CNM, Lone Tree OB/GYN & Midwives

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