Impaired Glucose Tolerance

Last Editorial Review: 3/29/2002

People with Impaired Glucose Tolerance (IGT) have blood glucose levels that are higher than normal but not yet diabetic. This condition is diagnosed using the oral glucose tolerance test (OGTT). After a fast of 8 to12 hours, a person's blood glucose is measured before and 2 hours after drinking a glucose-containing solution.

  • In normal glucose tolerance, blood glucose rises no higher than 140 mg/dl 2 hours after the drink.
  • In impaired glucose tolerance (IGT), the 2-hour blood glucose is between 140 and 199 mg/dl.
  • If the 2-hour blood glucose rises to 200 mg/dl or above, a person has diabetes.

As few as 1 to as many as 10 of every 100 persons with IGT will develop diabetes per year. The risk of getting diabetes rises as people become more overweight and more sedentary, have a stronger family history of diabetes, and belong to a racial or ethnic minority group.

For more, please read the Diabetes Mellitus article.

Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

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