Gestational Diabetes Test: What to Know Beforehand
Everything to Know About Taking a Gestational Diabetes Test
July 1, 2022

Everything to Know About Taking a Gestational Diabetes Test

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Everything to Know About Taking a Gestational Diabetes Test.
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Everything to Know About Taking a Gestational Diabetes Test

If you’re approaching the midpoint of your pregnancy, chances are you’ve heard about the gestational diabetes test (a.k.a. glucose test) that every pregnant person gets.

Before you schedule your appointment and head off to the lab, here’s what you need to know about gestational diabetes testing—plus a little extra info because we know you want to know it all.

What is gestational diabetes?

Gestational diabetes (or GDM) is a condition where a pregnant person’s body can’t properly regulate the level of glucose (sugar) in their blood, so it gets unhealthily high. This is mainly due to the hormones and weight gain of pregnancy and should go away after you deliver.

“While it doesn’t mean that you had diabetes before you conceived or that you will have diabetes after you give birth, we know that type 2 diabetes occurs more frequently in women after they have had GDM,” says Laura Hieronymus, doctor of nursing practice and VP of health care programs at the American Diabetes Association. That’s just one reason why gestational diabetes is important to detect, but also because it can lead to complications for both parent and baby, including high birth weight, preterm birth and health problems later in life.

The CDC estimates that 2% to 10% of pregnant people develop gestational diabetes, but even if you think you aren’t at risk, the symptoms can be tough to detect. That’s why every pregnant person gets a gestational diabetes test for each pregnancy.

When do you test for gestational diabetes?

The glucose test for gestational diabetes happens around 24 weeks to 28 weeks of pregnancy. But your healthcare provider may suggest that it be done sooner if you have a history of diabetes in your family or if you’ve been diagnosed as prediabetic in the past.

What are the types of gestational diabetes tests?

There are two strategies for gestational diabetes testing: a “one-step” strategy and a “two-step” strategy, Hieronymus says. They both involve having blood drawn before and after drinking a sweet glucose drink, but they differ slightly in the amount of blood drawn, the amount of fasting required and the amount of time they take. The one you end up with most likely depends on your healthcare provider and the lab they work with. Here are the steps for each strategy, according to Hieronymus:

One-step strategy:

  1. Fast for at least eight hours
  2. Blood is drawn to test your fasting blood sugar levels
  3. You’ll drink 75 grams of a sweet, Gatorade-like glucose solution
  4. Wait one hour (you’ll likely be told to stay in the clinic’s waiting room so they can monitor you; bring some reading material, your phone, your tablet or hope they have something good on TV)
  5. One hour after drinking the glucose solution, blood is drawn a second time to measure blood glucose
  6. Wait another hour
  7. Two hours after drinking the glucose solution (or one hour since the last blood test), a third blood draw is taken
  8. A diagnosis of gestational diabetes is made when any of the following blood glucose values are equal to or higher than the following:
  • Fasting: 92 mg/dL
  • One hour: 180 mg/dL
  • Two hours: 153 mg/dL

Two step strategy:

Step One (the “glucose challenge test” or “one-hour glucose tolerance test”):

  1. No fasting required (thank goodness!)
  2. An initial blood draw may or may not be taken
  3. You’ll drink 50 grams of the glucose solution
  4. Wait one hour
  5. One hour after having the glucose drink, a blood test will be taken to measure your blood glucose level. If the result is 130 mg/dL, 135 mg/dL, or 140 mg/dL, then the second step is recommended. Keep in mind: “The results used for Step One may vary between pregnancy health care providers,” Hieronymus says.

Step Two (the “glucose tolerance test” or “three-hour test”):

  1. Fast for at least eight hours
  2. An initial blood draw is taken to test for fasting blood sugar levels
  3. You’ll drink 100 grams of the glucose solution
  4. Exactly one, two, and three hours after having the glucose solution, blood is drawn to test blood glucose levels (that’s right, you’ll get poked four times with this step; once after fasting, and three times after drinking the glucose solution—all after 11 hours of no eating)
  5. A diagnosis of GDM is made when at least two of the following blood glucose values are equal to or higher than the following (Keep in mind: According to Hieronymus, some doctors will diagnose gestational diabetes if only one blood glucose value is equal to or higher than these numbers):
  • Fasting: 95 mg/dL
  • One hour: 180 mg/dL
  • Two hours: 155 mg/dL
  • Three hours: 140 mg/dL

What to eat before the gestational diabetes test

Whether you’re doing the one-step strategy or the two-step strategy, there’s going to be some fasting involved at some point. If you’re instructed to fast, don’t eat anything for at least eight hours before your test.

You can drink water if you’re fasting, but no coffee, tea or any other drinks, Hieronymus says.

If you’re not instructed to fast (i.e. you’re doing the one-hour glucose challenge test), you should eat your regular diet, so that if you’re required to do an initial blood draw, it’s as close to what it would normally be as possible.

How to pass the gestational diabetes test

People sometimes ask how to pass the glucose tolerance test. But here’s the truth: there’s no passing or failing. If you’re diabetic, the results will reflect that—and truly, that’s important for you and your baby, so you can get the treatment you need to prevent problems. And if you’re not, you’re not. So no trying to cheat the system here.

Tips on Taking the Glucose Tolerance Test

  • Schedule your appointment for the first thing in the morning. You’re not likely to worry about the fact that you’re fasting while you’re asleep. Then, you can get up, go immediately to your appointment and be done before lunch time.
  • Really do the fasting. “Be sure to avoid eating or drinking anything after midnight before the test,” Hieronymus says. It may seem like no biggie to have a midnight snack or a little bite of breakfast. But resist the urge! You really don’t want to end up with inaccurate or inconclusive results and have to do this gestational diabetes test all over again.
  • Drink water. Yes, you’re allowed to have small sips of water while you’re fasting. Hey, at least it’s something! But make sure it’s just water. “Do not drink any or eat anything, including coffee and other beverages until after the testing is completed,” Hieronymus says.
  • Ask your doctor about your medications. To make sure there’s no interference with your results, “Ask your provider ahead of time about any morning medications you take, and if taken before testing be sure you take them with water only,” Hieronymus says.
  • Keep yourself busy. Bring plenty to keep you occupied—a book, magazines, podcasts and/or music with earbuds. Three hours in a waiting room is really not fun without distractions, and there’s no guarantee they’ll have something good on TV in the waiting room.
  • Make your meal plan. You’re going to be ravenous and want to eat ASAP after that last blood draw. Plot out the nearest place to grab a quick snack or meal afterward. Or better yet, pack snacks and leave them in your bag or your car to grab as soon as you leave.

Gestational Diabetes Treatment

If you get diagnosed with gestational diabetes, it’s not the end of the world. But you will have to stay on top of things to keep yourself and your baby healthy. “Untreated [gestational diabetes] is unhealthy for a woman and her baby, [so] it is essential to start treatment quickly,” Hieronymus says. “The treatment for [gestational diabetes] aims to keep blood glucose levels equal to those of pregnant women who don’t have [gestational diabetes].” Gestational diabetes treatment includes:

  • Healthy eating. Your doctor will probably refer you to a nutritionist who will help create a healthy eating plan. This will include watching your carb intake (but not cutting carbs completely thankfully). We have healthy gestational diabetes eating tips here.
  • Exercise. Exercising at least 30 minutes a day, three to five days a week can go a long way in helping you control your blood sugar and prevent complications from gestational diabetes. It doesn’t need to be intense—gentle exercise like swimming and prenatal yoga can help. You might also find that taking a walk after a meal helps keep your blood sugar low.
  • Monitoring your blood sugar. It’s no fun having to prick your finger and test your blood sugar throughout the day. But this is a really important part of monitoring your gestational diabetes.
  • Extra OB visits. You’ll probably find your doctor wants to check in on you and baby more often because you have gestational diabetes. You may get more ultrasounds too. You’ll be busy, but it’s all to make sure baby’s still doing great in there. Plus, more ultrasounds means more peeks at your baby.

Hopefully, this information helps put your mind at ease as you prepare for your gestational diabetes test.

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