What is the Glucose Tolerance Test?

Nearly one in 10 women will develop gestational diabetes (GD) during pregnancy. As a result, the American Congress of Obstetricians and Gynecologists (ACOG) recommends practitioners use the glucose tolerance test in all prenatal patients.

How to prepare for the glucose tolerance test

glucose solutions for glucose challenge test

50 grams of glucose are used in the 1-hour test & 100 grams of glucose are used in the 3-hour test. Flavors vary.

The glucose tolerance test takes approx. one hour and will often be performed by your OBGYN between 24 and 28 weeks of pregnancy. If you have risk factors for gestational diabetes, your doctor may opt to perform the test in the first trimester. (Risk factors increase for people who are older than 30 years of age or are overweight, come from certain ethnic backgrounds, or have a history of diabetes or a prior history of GD, among other things.) The glucose tolerance test is done to evaluate your body's ability to process sugars during pregnancy. Listed below are the proper steps and precautions that need to be taken in order to ensure the test results are valid:

  • Do not eat after midnight the day before the exam.
  • Try to bring a light snack with you to the appointment to eat after your blood has been drawn.
  • When you arrive for your appointment, you will be given a sweet glucose solution (often called glucola) to drink.
  • Try your best to drink the entirety of the solution within five minutes.
  • Do not eat anything after drinking the glucose solution.
  • Do not drink any other beverages besides water after drinking the glucose solution.
  • Your blood will be drawn one hour after finishing the glucose solution.

Results and three-hour testing

The doctor will normally call you in a few days with the results of the test. If the test is abnormal, you will be asked to return to the office for a longer, three-hour glucose tolerance test (GTT). This test will mostly follow the same steps as the first except you you should fast for the eight hours prior to the scheduled appt.; in addition, your blood will be drawn upon arrival and again at each hourly interval after drinking the glucose solution.

What if you have gestational diabetes?

If you fail the single-hour test and two of the three three-hour tests, then your body may not be properly responding to insulin. Treatments for gestational diabetes are ultimately up to your doctor and particular situation but may include a healthy diet rich in protein and low in simple carbohydrates and regular exercise. Blood sugar levels may have to be regularly checked and insulin shots may need to be regularly administered.

While gestational diabetes is caused by hormonal changes and goes away following pregnancy, it can increase the risk of type II diabetes later in life. If left untreated, it could cause excessive baby weight or premature birth. There is also a higher risk of the baby being obese or developing diabetes later in life. However, there are measures you can take to lower your risk of getting gestational diabetes. 

Last Updated on: 10/03/2023 by Diane Paradise