Here’s What to Eat Before a Glucose Test

A glucose test is performed to evaluate your body’s ability to process sugars during pregnancy. Learn what diet changes you may need to make before the test.


During pregnancy, a condition known as gestational diabetes can develop, posing a risk to both mother and baby. To identify this condition early on, most healthcare professionals recommend glucose testing between 24 and 28 weeks of pregnancy.

A glucose test is routine test that measures a pregnant woman’s blood sugar (glucose) levels. The first of two tests is known as a Glucose Challenge Screening. This preliminary test requires no preparation or diet restrictions. During the screening, you’ll drink a sugary solution. One hour later, your blood sugar level is measured.

“If the test results are above normal, you’ll need to have further testing to determine the diagnosis,” says the Mayo Clinic.

If a woman tests positive during the initial screening, a second test known as a Glucose Tolerance Test may be performed. This test determines whether the body is using glucose effectively. If two or more readings come back abnormal, you may be diagnosed with gestational diabetes.

While my first glucose screening was a cinch, the second was nearly intolerable. I was not allowed to eat following dinner the night before. While this restriction would be fine for my non-pregnant self, an empty stomach while pregnant meant extreme nausea. Chugging the larger volume of the surgery glucose drink almost made me toss my cookies.

What the Experts Say

If your blood glucose from the initial test is too high, you will need to undergo a 3-hour glucose tolerance test, according to MedlinePlus. You cannot eat during the test and you cannot eat or drink anything (besides sips of water) for 8 to 14 hours prior to the test. Some physicians may recommend a special diet in the days leading up to the test.

Here’s what some experts have to say about glucose testing during pregnancy:

“Any woman might develop gestational diabetes during pregnancy. Some of the factors associated with women who have an increased risk are obesity, a family history of diabetes, having given birth previously to a very large infant, a stillborn, or a child with a birth defect, or having too much amniotic fluid.”

Understanding Gestational Diabetes, Diane Publishing Company


“The most commonly used screening test for glucose intolerance during pregnancy is given at 24 to 28 weeks of gestation and consists of a 50 g. 1-hour oral glucose challenge. Patients whose glucose value exceeds 140 mg/dL require a standard 3-hour glucose tolerance test using 100 g of glucose.”

Obstetrics and Gynecology, Charles R. B. Beckmann


“You do not need to fast before the 1-hour glucose test, but don’t have a doughnut on your way to the doctor’s office either. If there is excess sugar in your blood, your doctor will order additional bloodwork to determine whether you have gestational diabetes.”

Pregnancy: The Ultimate Week-by-Week Pregnancy Guide, Laura Riley


“A number of factors contribute to the development of diabetes during pregnancy. The body requires more insulin during pregnancy to meet increased metabolic demands. High levels of estrogen, progesterone, and human placental lactogen – all needed to maintain the pregnancy – increase insulin resistance, and more insulin is needed to overcome it.”

Total Nutrition: The Only Guide You’ll Ever Need, Victor Herbert


Loading Up on Carbs

Many health professionals recommend upping your carbohydrates in the days leading up to the glucose tolerance test. It’s ideal to eat a balanced diet of at least 150 g of carbs per day for at least three days before the test, according to WebMD.

Consuming a reasonable amount of carbs, such as bread, rice, cereals, potato, pasta, and various fruits and veggies, has been found to make the results of the glucose test more reliable.

In addition to the usual foods you eat, suggests choosing one item from List I and one item from List 2 below to boost your carb intake:

List 1

  • 2 slices of bread
  • 2 corn tortillas
  • 1 cup cooked noodles
  • 2/3 cups cooked rice

List 2

  • 2 large apples
  • 2 small bananas
  • 4 oz. raisins
  • 16 oz. apple or orange juice

Do you have a glucose test coming up? You may be wondering what you should eat to ensure accurate results. Ask your doctor if you’re unsure of what to eat or what not to eat before your glucose test.


Brandy Dishaw

Brandy is a content specialist and proud mother of two children. She enjoys writing engaging content on parenting, children’s health, and educational topics, and has been published on websites like Modern Mom, Yahoo! Shine, and With more than a decade of experience as a writer and mom, she combines research and personal experience to provide her audience with insight to the world of parenting.

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