Oral Glucose Tolerance Test

Glucose Challenge Test, Glucose Tolerance Test, OGTT (Oral Glucose Tolerance Test)

How To Prepare

Glucose challenge screening test for gestational diabetes

No preparation is usually needed for the screening test done during pregnancy. This test can be done at any time of the day, so, you do not need to limit food or fluids before the test.

Glucose tolerance diagnostic test

To prepare for the glucose tolerance diagnostic test:

  • Eat a balanced diet that contains at least 150 to 200 grams (g) of carbohydrate per day for 3 days before the test. Fruits, breads, cereals, grains, rice, crackers, and starchy vegetables such as potatoes, beans, and corn are good sources of carbohydrate.
  • Do not eat, drink, smoke, or exercise strenuously for at least 8 hours before your first blood sample is taken.
  • Tell your health professional about all prescription and nonprescription medicines you are taking. You may be instructed to stop taking certain medicines before the test.

The glucose tolerance diagnostic test may take up to 4 hours. Since activity can interfere with test results, you will be asked to sit quietly during the entire test. Do not eat during the test. You may drink only water during this time.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, or how it will be done. To help you understand the importance of this test, fill out the medical test information formClick here to view a form.(What is a PDF document?).


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Author: Caroline Rea, RN, BS, MSLast Updated: July 25, 2007
Medical Review: Caroline S. Rhoads, MD - Internal Medicine
Alan C. Dalkin, MD - Endocrinology

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Topic Contents
 Test Overview
 Why It Is Done
Arrow PointerHow To Prepare
 How It Is Done
 How It Feels
 Risks
 Results
 What Affects the Test
 What To Think About
 References
 Credits