What foods to avoid before glucose test

American Diabetes Association Professional Practice Committee. 2. Classification and diagnosis of diabetes: standards of medical care in diabetes-2022. Diabetes Care. 2022;45(Suppl 1):S17-S38. PMID: 34964875pubmed.ncbi.nlm.nih.gov/34964875/.

Committee on Practice Bulletins--Obstetrics. Practice Bulletin No. 190: Gestational diabetes mellitus. Obstet Gynecol. 2018;131(2):e49-e64. PMID: 29370047pubmed.ncbi.nlm.nih.gov/29370047/.

Landon MB, Catalano PM, Gabbe SG. Diabetes mellitus complicating pregnancy. In: Landon MB, Galan HL, Jauniaux ERM, et al, eds. Gabbe's Obstetrics: Normal and Problem Pregnancies. 8th ed. Philadelphia, PA: Elsevier; 2021:chap 45.

Metzger BE. Diabetes mellitus and pregnancy. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 45.

Moore TR, Hauguel-De Mouzon S, Catalono P. Diabetes in pregnancy. In: Resnik R, Lockwood CJ, Moore TR, Greene MF, Copel JA, Silver RM, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 59.

Last reviewed on: 4/19/2022

Reviewed by: John D. Jacobson, MD, Department of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

No dancing around the truth here. Find out what to eat for the glucose screening test, what to do for the best results, and a few helpful tips for testing day.

Gestational Diabetes:

Consistently high blood sugar levels discovered in pregnancy.
Also referred to as gestational diabetes mellitus.

I'll give you the bottom line up front, but stick around to understand the why behind it.

It's simple, Mama - 2-3 hours before the glucose test, eat what you would normally eat for that time of day. This will give you the best results!

Table of Contents Show

1. The Best Chance of Passing

2. What the Test Results Mean

3. Risks of Unmanaged Gestational Diabetes

4. Treatment

5. Early Glucose Screening

6. 1-Hour Glucose Test Procedure

6.1. False Positives

7. What to Eat Before the Glucose Test

8. 3-Hour Test Procedure

9. OGTT Controversy

10. Gestational Diabetes Diagnosis Criteria

The Best Chance of Passing

The best chance you have of passing the test is to eat a healthy diet throughout pregnancy that focuses on:

  • nutrient-dense foods
  • lean meat
  • fruits and vegetables
  • complex carbohydrates
  • whole grains
  • portion control
  • lots of water

Healthy lifestyle changes that also influence blood sugars are regular movement and exercise, adequate sleep, and minimal stressors.

But the glucose test is less about passing and more about a healthy pregnancy.

What foods to avoid before glucose test

What the Test Results Mean

We have to address the mindset around the gestational diabetes test, because the terms "pass" and "fail" have created a fear of testing, and stigmatized moms.


The gestational diabetes test is NOT a grade of your health, body, or pregnancy! Moms that "pass" are not rewarded, and moms that "fail" are not penalized.

Instead, the test is a discovery of whether or not your body produces enough insulin to maintain blood sugars at safe levels. It's knowing and understanding what's happening to your body as you journey through this pregnancy.

The gestational diabetes test is NOT a grade of your health, body, or pregnancy!

Risks of Unmanaged Gestational Diabetes

If you have gestational diabetes and it goes undiagnosed, or untreated, the risk of pregnancy complications is increased. For mom, this includes high blood pressure, preeclampsia, and c-section. Baby is subject to macrosomia (large baby or excessive birth weight), shoulder dystocia, jaundice, low blood sugars, and stillbirth.

Long term health risks include problematic blood sugars for mom and baby, resulting in a diagnosis of diabetes.

Each of these outcomes is possible in non-gestational diabetes pregnancies as well, but with GDM, you are at higher risk.


Managing high blood sugars with only dietary changes and exercise is ideal, but it's not always the best option depending on the circumstances.

Medications are available; a common one being Metformin. When diet and exercise aren't effective, medications are next in line of treatment, but meds come with side effects.

What foods to avoid before glucose test

If medications don't work out, insulin injections are next in line. Some moms have to, or choose to, take insulin from the beginning to keep blood sugars safe.

Discuss options with your health care provider to determine what is best for you.

Early Glucose Screening

Normally, your healthcare provider will test you for gestational diabetes between 24 and 28 weeks of pregnancy with the Oral Glucose Tolerance Test (OGTT).

Sometimes, early testing takes place if you have:

  • had gestational diabetes in a previous pregnancy
  • a family history of diabetes
  • multiple risk factors

It's a good idea to test early, and some health care providers test every mom early as a best practice, because the earlier it's detected, the better for mom and baby.

The great thing about testing early is that it's done during initial bloodwork at the first prenatal appointment. It requires no special effort from you. Best of all, you don't have to drink the OGTT glucose drink...yet.

What foods to avoid before glucose test

Here's the catch - If you test early and your blood glucose levels are normal, the doctor will still test you during the 24 to 28 week period with the OGTT.


Insulin resistance is natural in pregnancy, and 24 to 28 weeks is normally when blood sugars start to rise.

On the other hand, if you test early and your blood glucose levels are already high, the doctor will likely treat you as a gestational diabetic for the remainder of pregnancy.

1-Hour Glucose Test Procedure

Your health care provider will give you the glucola drink. Some providers allow you to take it home, and some require you to drink it at your appointment.

If you are required to drink it at the appointment, plan to be there over an hour.

It has to be consumed within 10 minutes. The time you finish is recorded; then your blood is tested one hour later. This blood test will likely be a finger prick with a handheld glucose monitor in the doctor's office.

Eating prior to the 1-hour test is necessary to reduce the chances of a false positive or false negative.

What foods to avoid before glucose test

False Positives

The purpose of the test is to see how your blood sugar reacts to pure glucose without other influencing factors.

This is why it's important to eat 2-3 hours before the 1-hour test. In 2-3 hours you will have digested your meal, and blood sugars returned to normal (normal for you). If you wait to eat 1 hour before the test, your body will still be processing the meal, and it will influence what happens to your blood sugar when you drink the glucose solution. This could produce a false positive or false negative.

If you do not eat before the test, your blood sugars might be in a yo-yo (up and down) state to compensate for not having any food. This could also give an inaccurate result.

Moms with gestational diabetes can, and do, have healthy babies.

What to Eat Before the Glucose Test

Now that you know results can easily be skewed, you can see how eating what you would normally eat for that time of day is the best option.

Attempting to "cheat" for a positive result will give you inaccurate information and put you and baby at increased risk for complications.

Not changing a thing about what you eat is how you will get the most accurate results.


  • Eat before the 1-hour test
  • Eat 2-3 hours before the test
  • Eat what you normally eat

3-Hour Test Procedure

The three-hour glucose test requires you to fast at least 8 hours. This test requires 4 blood draws. The procedure is as follows:

  • Arrive at the appointment in a fasting state
  • 1st blood draw
  • Consume the drink in 10 mins
  • 2nd blood draw one hour later
  • 3rd blood draw one hour later
  • 4th blood draw one hour later

You will be at this appointment for 3-4 hours. During this time you cannot leave or eat. Some places don't even allow you to drink water.


  • Bring a granola bar or other quick snack that you can scarf down after the last blood draw.
    (By the end of the appointment your blood sugar will have likely crashed: you'll feel low-energy, light-headed, and hungry!)
  • Make the appointment as early as possible.
    An afternoon appointment is far too long to go without eating, unless that's normal for your schedule.

OGTT Controversy

There is controversy about the glucola drink containing dyes and toxins. If you, like many other moms, take issue with this, alternative testing options are available.

It's worth knowing the alternative methods, because drinking the glucola drink is harder than it sounds. Many find the taste displeasing, and it must be finished within 10 minutes of starting. If you can't drink it within 10 minutes, and keep it down (not throw up), you have to try again a different day.

(There are a handful of flavors to pick from. Reportedly, the lemon-lime flavor causes less discomfort and tastes better.)

Side-by-Side Glucose Tests Review

Early Testing (HbA1c)1 Hour Test3 Hour TestTimeframe1st trimester24-28 weeks24-28 weeksFasting Required--YesGlucose Drink-YesYesBlood Draws11 (finger prick)4

Gestational Diabetes Diagnosis Criteria

If you've heard that moms have different cut-off numbers, like 90 as opposed to 95 for fasting, it's because different governing organizations determine the criteria.

Many doctors abide by the American Congress of Obstetricians & Gynecologists (ACOG) standards for diagnosis:

1-Hour Test - 50 grams of glucose consumed in 10 minutes and blood tested 1 hour later

  • No diagnosis if reading is 139 or less.
  • If reading is between 140 and 199, proceed to the 3 hour test.
  • If reading is 200 or more, gestational diabetes is diagnosed.

3-Hour Test -100 grams of glucose consumed in 10 minutes from a fasting state

  • 1st blood draw (fasting blood glucose level) should be 94 or less.
  • 2nd blood draw should be 179 or less.
  • 3rd blood draw should be 154 or less.
  • 4th blood draw should be 139 or less
  • If any TWO readings are above range, gestational diabetes is diagnosed.
What foods to avoid before glucose test

The American Diabetes Association (ADA) and the International Association of Diabetes and Pregnancy Study Group (IADPSG) recommend the following:

What should I avoid eating before my glucose test?

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.

Does what you eat night before glucose test affect results?

Fasting before certain blood tests is important to help make sure that your test results are accurate. The vitamins, minerals, fats, carbohydrates, and proteins that make up all food and beverages can impact blood-level readings, clouding the results of your test.

What should I eat the night before my 3 hour glucose test?

YOU MUST BE FASTING for this test. DO NOT eat or drink anything except WATER for at least 8 hours before the test. You may drink plain water ONLY. Do NOT drink coffee, tea, soda (regular or diet) or any other beverages.

What should I eat before and after a glucose test?

Preparations for Postprandial Glucose Test For a fasting glucose test, you need to fast for at least 8 hours before giving the sample for the test. After this, you need to eat a meal containing around 75 grams of carbohydrates.