What is an oral glucose tolerance test?

The oral glucose tolerance test (OGTT) measures and determines the body’s response to glucose. It identifies how our body processes the amount of sugar, which is necessary to diagnose diabetes. This type of test often determines if gestational diabetes, a condition that occurs during pregnancy, has developed.

Other than gestational diabetes, OGTT is also used for the following tests:

The oral glucose tolerance test has two types. These types are helpful in the screening process for diabetes. Consider the following:

  • 2-hour oral glucose tolerance test – This test involves two blood draws but is only used for non-pregnant adults for diabetes and prediabetes diagnosis.
  • 3-hour oral glucose tolerance test – This involves four blood draws specifically designed to screen for gestational diabetes.

Like other blood sugar tests, the OGTT has advantages and disadvantages.

The advantages are:

  • Compared to the fasting plasma glucose test, it is more sensitive to blood sugar measurement.
  • OGTT helps detect blood sugar dysfunction early.
  • OGTT is the only test that diagnoses a dysfunction in glucose tolerance.

On the other hand, OGTT becomes a disadvantage when:

  • The test is very time-consuming. It will require people to fast for a longer period.
  • Some factors can affect how this test functions, such as medications and underlying illnesses.

How to prepare for the test?

As mentioned, there are two types of OGTT. Before your test, your healthcare professional will provide you with instructions on how to prepare for the test.

If you test for type 2 diabetes, you need to drink eight ounces of glucose solution that contains 75 grams of sugar. After two hours, your blood glucose levels will be measured by taking a blood sample from your vein.

For gestational diabetes, the healthcare professional will ask you to fast eight hours prior to your testing. This is a requirement to obtain a fasting blood sugar result. In the lab, you will drink 8 ounces of glucose solution that contains 100 grams of sugar. After two to three hours, your blood glucose will be tested.

If you are diagnosed with gestational and type 2 diabetes, you need to take measurements immediately by taking oral medications. These oral medications can help lower blood sugar and prevent diabetes-related complications.