woman using glucose meter on her finger

Gestational diabetes: Glucose challenge test

Gestational diabetes is a serious pregnancy complication that can affect the health of both mom and baby. There are risk factors, but many people with no known risk factors develop gestational diabetes too. Because of this, healthcare providers recommend every pregnant person has screening and testing for it with a test called the Glucose Challenge Test (GCT) and, if needed, a Glucose Tolerance Test (GTT).

What is gestational diabetes?

Gestational diabetes is the temporary onset of diabetes, a condition that affects your body’s ability to maintain safe blood sugar levels, that sometimes occurs during pregnancy. Gestational diabetes is among the most common pregnancy complications, and although there is no magic cure, most of the time, it can be managed by diet, physical activity and lifestyle. Some people will also need medication. Gestational diabetes goes away with birth, but people who have had gestational diabetes are at higher risk for developing Type 2 diabetes postpartum or later in life.

How do healthcare providers detect gestational diabetes?

Gestational diabetes generally doesn’t develop until the second half of pregnancy, so most healthcare providers ask pregnant people to take the initial screen, the Glucose Challenge Test, around Week 24. If this result is high, you’ll probably have to take the Glucose Tolerance Test shortly thereafter to confirm a diagnosis. Some people at higher risk of gestational diabetes will be asked to take the GCT even earlier than Week 24. 

Glucose Challenge Test

It can help to know what to expect at the GCT again, generally administered between weeks 24 and 28 of pregnancy. Prior to the test, you can usually eat and drink normally until about an hour before going in. Making that last meal a high-protein one, and staying hydrated with water, can help you feel good after the test.

This can be especially important for people who are still struggling with pregnancy nausea. When you arrive, your healthcare provider will ask you to drink a sweet and syrupy drink called glucola that tastes a lot like a flat soda. It’s made with an exact amount of glucose to see how your body responds. You may have a choice of flavors or even do this part at home. Pro tip? It often tastes better cold! You’ll have about 10 minutes to drink this small drink, and then you’ll wait for an hour before you’ll have a blood sample drawn from your arm. If your blood sugar level is high, you’ll be notified and your healthcare provider will probably recommend the Glucose Tolerance Test.

Glucose Tolerance Test

Prior to taking the Glucose Tolerance Test, your healthcare provider will ask you to avoid eating for at least the eight hours leading up to the test. Once there, you’ll have an initial blood glucose level checked, and then you’ll be asked to drink a similar glucola drink to the GCT.

Your blood will then be tested 1, 2, and 3 hours after you’re done with the drink. This test gives your provider several results to consider before making a diagnosis (or not) of gestational diabetes.


Although gestational diabetes can be a serious complication of pregnancy, detecting it early and getting support for keeping blood sugar levels normal means that most people who develop it give birth to perfectly healthy babies and remain healthy themselves. It is most important to follow your healthcare provider’s instructions if you are diagnosed with gestational diabetes in order to keep you and your baby healthy and safe.

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