Patient Preparation and Expectations

The glucose tolerance test is used to diagnose diabetes. This test should be done in the morning after an overnight fast of at least 8 hours and after at least 3 days of unrestricted diet (> 150 grams of carbohydrate per day) along with unlimited activity. The patient should remain seated and abstain from smoking throughout the test.  For patient safety and to ensure required specimen collection times are met, persons undergoing this procedure should remain on the hospital grounds, preferably in the nearest waiting area, during the entire testing period. You will be asked to drink a sweet liquid and have your blood drawn several times. The test may last 1.5 -5.5 hours depending on your physician’s orders.

The Test Procedure

  1. A blood sample is drawn.  The results of this test must be obtained before the test continues.  There will be a waiting period of about 30 minutes.  If the test results are suitable, the test will continue.
  2. You will be given a glucose drink. You will have 5-10 minutes to drink it (the quicker you finish the drink, the earlier the test can commence).
  3. You cannot eat or drink anything (except water) during the test.
  4. Each hour after the glucose drink is finished; another blood sample will be drawn until the test is finished.