How To Pass The Glucose Tolerance Test In Pregnancy (What To Eat?)

So you’re 24+ weeks and you were told to take the glucose test.

If you’re anxious, you’re not alone. It can be a very stressful test.

In this post, you’re going to learn how to pass the glucose tolerance test in pregnancy.

Specifically, you need to make sure that you eat a well-balanced diet leading up to the test, and minimize other specific foods from your diet.

You’ll also learn answers to questions like what you should eat before taking the test.

Let’s get started.




Although I am a doctor, I am not your doctor. This information is for informational purposes only and should not substitute the advice from your healthcare professional. Please read my full Disclaimer for more information. Also, this post may contain affiliate links: meaning I may receive a commission if you use them.

Ok, moving on.

What Is The Glucose Test You Take In Pregnancy?

The glucose test is basically a simple way to determine how your body processes sugar in the third trimester of pregnancy.

In other words, it is a screening test to look for gestational diabetes. This screening test is known as the glucose challenge test.

You will be asked to drink a solution that contains a certain amount of glucose and have your blood test taken 1 or 2 hours later.

The glucose challenge test can be done between 24-28 weeks of gestation, which is about 6 months. 

If you fail, you will then need to perform a glucose tolerance test.

More on that later.

Do I Need To Take The Glucose Test?

Yes. The American College of OBGYN recommends that ALL pregnant women be screened for gestational diabetes. If you are at high risk, you will be screened twice- once in the first trimester, and again in the third trimester.

You are high risk if you are:

  • Obese
  • Have a strong family history of diabetes
  • Had gestational diabetes in a prior pregnancy

Do I Need To Be Fasting For The Pregnancy Glucose Test?

There are two different tests that you can do. 

  • There is a 1 hour 50-gram glucose challenge test
  • and a 2 hour 75-gram challenge test

Different clinics will use one or the other. In my clinic, we use the 50-gram 1-hour test.

The 50-gram test is easier as you don’t have to be fasting, and we only take one blood test 1 hour after the ingestion of the glucose.

For the 75 gram test, you need to be fasting, and you have to have your blood taken three times.  Once fasting, once after an hour, and again after 2 hours.

Most providers use the 1-hour test, so the remainder of this article will be about the 50-gram glucose challenge test.

How Do I Prepare For My 1 Hour Glucose Test?

Like I said before, you don’t need to be fasting for the 1 hour 50-gram test.

It is okay to have your typical normal breakfast before the test. That’s because it’s important to get an accurate representation of how your body handles sugar on a day to day basis.

Otherwise, try and get a good night’s sleep the week before the test.

Sleep deprivation can increase cortisol levels, which can also affect your blood sugar levels. 

More on that later.

What Is The Normal Range For the 1 Hour Glucose Test?

A normal test result for the 1 hour 50-gram glucose test is lower than 140 mg/dL. 

  • Some clinics will use a lower threshold of 130 mg/dL. This lower level is used if the population is at high risk of gestational diabetes.

If you happen to have a value greater than 200 mg/dL, then you meet the criteria for the diagnosis of gestational diabetes.


If you take the 2-hour 75g challenge, a normal result is less than 180 mg/dL at the 1-hour mark, and less than 155 mg/dL at the 2-hour mark

In addition, your fasting blood glucose level should be lower than 95 mg/dL for the 2-hour test.

How Do You Pass The Glucose Challenge Test When Pregnant?

There is nothing special you can do right before the test to make sure you pass.

The best thing you can do is eat a well-balanced diet for the months leading up to the test

Note that I said months. 

You cannot change your result by changing your diet the day or the week before your test. Eat a well-balanced diet as soon as you become pregnant (and for the rest of your life!).

A well-balanced diet is rich in fruits, vegetables, whole grains, healthy fats, and protein.


The second thing you should do is avoid eating simple carbohydrates during your pregnancy

Simple carbohydrates are foods that tend to cause large spikes in your blood sugar levels.

Exposing your baby to these elevated sugar levels can cause a lot of fetal complications

So which foods should you avoid?

The ones that have a high glycemic index. See below for specific examples.

The last thing you need to do is to try and get adequate sleep for the majority of your pregnancy

I love sleep :).

It is so important for so many things. Including your sugar levels.

Let me explain a little further.

Can A Lack of Sleep Affect Fasting Blood Sugar?

Yes. A lack of sleep can affect your fasting sugar. Sleep deprivation is a highly stressful situation for your body.

High stress = high epinephrine and high cortisol levels.

These hormones can increase insulin resistance, and increase the available amount of sugar in your blood.

In other words, a lack of sleep can impact how your body metabolizes sugar.

There is growing evidence that sleep loss and diabetes are related.

What Not To Eat The Night Before A Glucose Test

I know that you still want a list of foods you should avoid before the test. If your glucose challenge test is tomorrow, it is a good idea to avoid high glycemic foods for at least 8 hours before the glucose test.

These foods include 

  • White rice
  • White bread
  • Baked goods with White flour 
  • White potatoes
  • Soda
  • Juice
  • Breakfast cereal

Instead, go for whole grains such as steel-cut oats, brown rice, sweet potatoes, and leafy green vegetables.

Is There Anyway To Cheat A Fasting Blood Sugar Test?

There is no way to cheat the test. You won’t be able to manipulate the way your body processes sugar unless you have access to specific medications.

I won’t go into any more details because YOU SHOULD NOT try to cheat the glucose pregnancy test.

This test is really important if you care about the health of your pregnancy and baby. We need to be able to see how you’re body processes sugar.

If you have gestational diabetes, and try to falsify your results, you will increase

  • the risk of your baby having birth defects
  • the risk of your baby being extremely large 
  • the risk of developing preeclampsia
  • the risk of having a c-section
  • And so much more 

So get tested and do it right!

What Does The Glucose Test Taste Like?

The glucose drink is very very sweet. It will taste like flat soda or really concentrated kool-aid.

It often comes in two flavors- cherry and orange.

Some women may even feel symptoms of nausea after drinking it.

Sorry, it’s disgusting. 

Can You Walk Around During The Glucose Tolerance or Challenge Test?

Yes, you can walk around during the glucose test. A normal amount of walking shouldn’t impact the test results.

With that being said, don’t go for a run, or do 200 squats and push-ups, as this can make the results unreliable :).

How Common Is it To Fail The 1 Hour Glucose Challenge Test?

In general, anywhere from 15-25% of women will fail the glucose challenge test. But keep in mind that failing the 1-hour test does not give you the diagnosis of gestational diabetes.

Only about 20% of women who fail the screening test (with a score of 135-143) will actually have the condition.


According to the CDC, the prevalence of gestational diabetes is about 2-10%.

But failing the test should raise some red flags that you need to pay attention to your diet.

What If I Fail The 1 Hour Test?

The 1-hour test is just a screening test! If you fail the 1 hour 50-gram test, you will then need to take a 3 hour 100-gram glucose tolerance test.

This test is much more involved and will be scheduled in about 1 week after your screening glucose challenge test.

What Is The Difference Between The 1 Hour Challenge and the 3 Hour Glucose Tolerance Test? 

The 1-hour test only requires one blood draw after drinking 50 grams of glucose, whereas the 3-hour test requires a fasting blood draw, and 3 additional blood draws, after drinking 100 grams of glucose.

The 1-hour test is a screening test, while the 3-hour test is a confirmatory test.

Let me explain.

For the 1 hour test, you’ll drink 50 grams of glucose and have your blood taken 1 hour later. You do not need to be fasting for it. Like I mentioned previously, this is a screening test that all pregnant women undergo.

If you test positive on the 1 hour screening test, you will undergo the 3 hour confirmatory test.

The 3 hour test involves a fasting blood draw followed by drinking 100 grams of glucose. You will then have your blood taken after 1 hour, 2 hours, and 3 hours later.

Can You Drink Water During The 3 Hour Glucose Test?

Yes, you can drink water during the 3-hour glucose tolerance test. 3 hours is a long time to not eat or drink anything, especially if you were already fasting for at least 8 hours first.

But DO NOT eat or drink anything else. Otherwise, your blood sugar levels will be even higher.

What If I Failed The 3 Hour Glucose Test?

If you fail the 3-hour glucose test, you have the diagnosis of gestational diabetes.

A failing score is considered when you have 2 or more values in these ranges:

  • Fasting > 95mg/dL
  • 1 Hour > 180 mg/dL
  • 2 Hour > 155 mg/dL
  • 3 Hour > 140 mg/dL

This is a very serious condition that requires very close monitoring of your blood sugar levels every single day.

If you don’t, you are putting your own life and your baby’s life at risk.

What Are The Warning Signs of Gestational Diabetes?

Unfortunately, gestational diabetes is often silent. This means that you may not see warning signs or symptoms of the disease. That is why we screen every single pregnant woman, regardless of risk factors.

A high amount of weight gain during pregnancy may be one of the only signs you may see. 

I will write an entire post on gestational diabetes in the future, so stay tuned.

Is There An Alternative Way To test For Gestational Diabetes?

Yes. If you do not want to drink the glucose solution for one reason or another, there is another way we can test you for gestational diabetes.

It would involve you actually checking your blood glucose through finger sticks four times a day for an entire week.  This will give us a good idea of how your body is processing the foods that you eat.

Again, don’t try to manipulate this test in any way.  For example, don’t try to eat really healthy for that week, then go back to eating your normal diet the subsequent week.

Just to be safe, your doctor may have you check your finger sticks for 2 or more additional weeks just in case.

Final Thoughts

The glucose test in pregnancy is an easy way to check your body’s ability to tolerate glucose loads.

There’s no way to cheat this test and you should prepare for it by eating a well-balanced diet as soon as you find out you’re pregnant.

If you fail the test, make sure that you follow up very closely with your doctor to prevent serious complications.

Good luck.

Did you fail your glucose test? 

What did you do to prepare for it?

Comment below and let me know!

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Brittany N Robles, MD, MPH, CPT

Brittany N Robles is a full-time OBGYN, a NASM certified personal trainer, and health & fitness expert. She holds a Masters of Public Health degree in maternal health with a special interest in exercise and nutrition. She is also the co-author of The White Coat Trainer. Learn more about her here.

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