Testing Information

Oral Glucose Tolerance Test

A doctor, usually using an oral glucose tolerance test, diagnoses diabetes.This is a special blood test that shows how well the body uses and absorbs glucose.

Talk to your doctor about how often you should be tested. How frequently you are tested for diabetes depends on your age and risk factors for the condition.

  • If you are 45 years old or older, you need to get tested for diabetes, even if you do not have any risk factors.
  • If you are younger than 45 and have one or more risk factors, you should also get tested.
  • After the age of 45, people should be tested for diabetes every three years.

If you are scheduled for an oral glucose tolerance test, your doctor or nurse will most likely give you written instructions for what to do before and after the test, and what to expect during the test. The instructions may include the following:

  • For three days before the test, eat an unrestricted diet high in carbohydrates and limit alcoholic beverages.
  • Fast for 12 hours before the test.
  • The test will last about three hours.

How the test works:

  1. You may be asked to provide a urine sample.
  2. You will be given a liquid to drink, which contains glucose. The liquid will cause your blood glucose level to rise.
  3. Samples of blood and urine may be taken regularly to measure glucose levels.

During the oral glucose tolerance test, some people feel:

  • Nausea
  • Stomach discomfort
  • Headache
  • These side effects usually go away quickly.