It's one of the most talked-about prenatal testing milestones when you're pregnant: the glucose screening, sometimes called the "sugar test" or the "glucose challenge test." Administered to most expecting moms between weeks 24 and 28 of pregnancy (give or take, depending on whether they're considered high-risk), its ultimate goal is to check for a very treatable condition: gestational diabetes.
The glucose screening test and, if necessary, the follow-up glucose tolerance test are performed to detect gestational diabetes (GD) and get moms the treatment and care they need for the rest of their pregnancies.[1] Most of the time, the results are ultra reliable. Sometimes, however, they're off.
Some research suggests that about 15 percent of women get a false-positive on their glucose screening and other studies say the number may be as high as 66 percent. In other words, they test positive for elevated blood sugar levels, but they don’t actually have gestational diabetes.
So why the discrepancy between what the test shows and the number of women who actually have GD? Though a number of factors may contribute, one possible answer is that some expectant moms test positive simply because of what they ate beforehand.
Here’s what should be on the menu before your glucose screening to boost your chances of passing it with flying colors.
What to eat before the glucose test
When you eat, your body breaks down carbs into glucose (or sugar), which is a main source of energy. During pregnancy, two types of glucose tests can check your blood sugar levels to detect and diagnose gestational diabetes. Each requires a different eating strategy, and usually only those who don't pass the first test are given the second one.
Glucose screening test
Between weeks 24 and 28 of each pregnancy (and possibly sooner, if you have a higher risk of gestational diabetes), your doctor will conduct a glucose screening, usually in the morning. During this screening, also known as the one-hour or two-step glucose test, you’ll drink a sugary beverage similar to flat soda and have your blood drawn an hour later to check the glucose levels in your blood.
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Don't make the mistake of eating a super sweet or simple-carb-laden breakfast[2], or skipping the morning meal altogether, before this first GD screening, as either can seriously throw your sugar levels out of whack. Instead, make sure you have a balance of healthy carbs and protein the night before and the morning of the glucose test.
Foods that serve up “good" or "complex" carbs are higher in fiber and take longer for your body to digest. They enter your bloodstream more gradually, so you won’t have those pesky blood sugar spikes. Complex-carb foods include:
- Whole grains, like whole wheat bread and oatmeal
- Vegetables, including non-starchy veggies like tomatoes, cucumbers, broccoli, leafy greens and green beans
- Fresh fruit, like berries, apples and watermelon
- Legumes in the form of chickpeas, black beans, kidney beans and lentils, to name a few
For long-lasting energy, balance your meal with protein-filled foods including dairy, nuts, fish or lean meat like poultry.
Here are some healthy breakfasts that may help you pass the glucose screening on the first try:
- Whole wheat toast topped with natural peanut butter or mashed avocado
- Plain Greek yogurt with blueberries
- Oatmeal made with low-fat milk and topped with fresh berries
- Broccoli and cheddar cheese omelet
- Tofu scramble with spinach and Swiss cheese
- Whole wheat burrito filled with scrambled eggs, beans and tomatoes
It’s also a good idea to watch what you eat before your regular prenatal appointments. That’s because every time you see your practitioner while you're pregnant, you’ll likely have to pee in a cup to monitor the sugar levels in your urine (another way to help detect GD).
Glucose tolerance test
If your blood sugar levels on the glucose screening are too high, it could mean your body isn’t producing enough insulin to process the extra glucose your system makes during pregnancy. You may need to go back for a glucose tolerance test, sometimes called the one-step test or three-hour glucose test.
This time, you’ll have your blood taken when you first arrive, after fasting ahead of time. You’ll then down a sugary, flat-soda-style drink again and have your blood drawn three more times: one hour, two hours, and three hours later. For the glucose tolerance test, you'll need to avoid eating for eight to 14 hours before your scheduled appointment.
How to pass the glucose screening
For the best results before your one-hour (or two-step) glucose screening, try to:
Eat breakfast
The morning of your appointment, have a healthy and not-too-copious breakfast containing a balance of complex carbohydrates and protein. (Remember, if you’re doing the glucose tolerance test, you’ll need to fast for at least eight hours beforehand. Not sure which test you’re taking? Confirm with your doctor.)
Avoid sugars and refined carbs
Don’t eat high-sugar foods or simple carbs (including refined grains) the morning of your glucose screening. The body breaks these foods down quickly, leading to a spike in blood sugar levels. That means avoiding breakfast favorites like:
- Orange juice and other fruit juices
- Sugary granola
- Refined cereal
- Sweetened toppings like jam or syrup
- Pancakes, waffles and French toast
- Donuts
- White bread
- Many other breakfast treats made with refined white flour, like banana bread, croissants, muffins and pastries
Take a walk
If you can, try to squeeze in a 10- to 15-minute walk after breakfast and before the screening, which can help get your blood sugar levels in check.
If you don’t pass the glucose screening
On your glucose screening or regular urine tests, it’s possible to get a positive test result that your doctor considers to be "medically insignificant" — meaning it has no impact on your growing baby. But it's still a good reminder to ask your doctor for healthy eating tips.
If your test does come back positive and you wind up being diagnosed with gestational diabetes, remember that the condition is usually easily managed (often with diet modifications only) and goes away soon after you give birth.
In the meantime, your doctor or midwife will ask you to monitor your blood sugar a few times a day and keep track of what you eat. Other strategies you'll be given to help keep your levels stable: cutting back on sugary, processed foods and loading up on meals that balance complex carbs with protein and incorporate plenty of pregnancy-friendly foods.
Frequently Asked Questions
How can I pass the glucose test?
There's no way to guarantee you'll pass the glucose screening test, but you're more likely to get a good result if you first eat a light breakfast that's high in protein and low in sugar, then take a quick walk. If you're completing the glucose tolerance test, you'll need to fast for eight hours beforehand for the most accurate results.
What should I do if I fail the glucose test?
If you fail the glucose screening, meaning you test positive, your doctor or midwife will typically order a glucose tolerance test to confirm. If you also fail the glucose tolerance test, your provider will talk to you about next steps. Often, you'll need to manage your diet and track your blood sugar. While it can be intimidating to get a gestational diabetes diagnosis, know that GD is usually easily managed and will go away shortly after your baby arrives.
What is the glucose test?
The glucose test is a routine screening given to pregnant women to check for gestational diabetes. The glucose test can also refer to the tolerance test, which is a lengthier test that can determine whether you have gestational diabetes if you fail the glucose screening. The test typically consists of drinking a sugary beverage provided by your healthcare provider and then getting blood drawn at specific intervals to check your blood sugar.
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