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  • Writer's pictureLisa Grossman, RN, IBCLC

Glucose Tolerance Testing during Pregnancy

Glucose Tolerance Testing (GTT) is a routine screening blood test completed during pregnancy. During pregnancy a condition called Gestational Diabetes Mellitus (GDM) or Gestational Diabetes can develop. This can occur as a result of hormonal, physiological and/or metabolic changes that occur during pregnancy leading to insulin sensitivity or resistance. Your doctor will order this test to be completed sometime between the end of your second trimester and the very beginning of your third trimester, typically between weeks 24 - 28 of pregnancy.

Depending upon your doctor and/or lab, you will be told to fast for a specified period of time leading up to the test. You will likely be given a beverage containing a specified concentration of glucose and will be told exactly when to drink it.

Fair warning, these drinks don't always taste that great and make some people feel nauseous or even throw up. If you throw up your doctor will need to determine how to proceed with the testing. You may need to repeat the test again as vomiting could effect the results of the test. If you are able to tolerate the drink, your blood test will be timed around the completion of the drink.

The blood test is typically completed 1 hour after the completion of the drink. You are not to eat or drink anything else prior to your blood draw. It may take a few days for the lab results to process. If your results are "within normal limits" there is typically no need to modify your diet, complete further testing/monitoring or take medication(s)/insulin. If your results read "high"then your doctor will advise you regarding the next steps, which typically require a 3 hour Glucose Tolerance Test.

Here are some helpful links and studies that discuss this topic further:

Normal Pregnancy - A State of Insulin Resistance

(Published by the Journal of Clinical & Diagnostic Research)

The American College of Obstetricians and Gynecologists

The American Diabetes Association

Thank you for taking the time to read my blog!


Lisa Grossman, BSN, RN, PHN, IBCLC, CLC, CLEC

Owner, South Bay Baby Care Nursing Services, Inc.

**This blog post is meant to serve as an educational opportunity and is not meant to diagnosis or treat any medical condition(s). Please consult with your medical practitioner if you have any personal questions related to this topic.

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