Our Glucose tolerance test Main Article provides a comprehensive look at the who, what, when and how of Glucose tolerance test

Definition of Glucose tolerance test

Type 2 Diabetes Slideshow Quiz: Are You At Risk for Diabetic Nerve Pain? Diabetes and Foot Problems Slideshow

Glucose tolerance test: A blood test done to make the diagnosis of diabetes mellitus. The test may also be done for other purposes such as to diagnose hypoglycemia (low blood sugar) or a malabsorption syndrome in which sugar is not absorbed properly through the intestines into the bloodstream.

The test was designed originally to determines the tolerance for the sugar glucose. "Tolerance" refers to the body's ability to handle (tolerate) glucose. However, the test is not that simple. The test depends on a number of factors including the ability of the intestine to absorb glucose, the power of the liver to take up and store glucose, the capacity of the pancreas to produce insulin, the amount of "active" insulin it produces, and the sensitivity of the cells in the body to the action of insulin.

For the test, you fast overnight and then are given a specific amount (100 grams) of glucose by mouth and then your blood glucose levels are monitored for 3 hours. Normally, the blood glucose should return to normal within 2 to 2½ hours. The outcome of the test may indicate:

• Normal glucose tolerance
• Abnormal glucose tolerance
  • Depressed glucose tolerance -- in which the blood glucose peaks sharply before declining slower then usual to normal levels -- as in:
    • Diabetes mellitus
    • Hemochromatosis (iron overload disease)
    • Cushing syndrome (too much cortisol ["cortisone"] hormone)
    • Pheochromocytoma (adrenaline-producing tumor)
    • Central nervous system lesions
  • Increased glucose tolerance -- in which the blood glucose levels peak at lower than normal levels -- as in the:
    • Malabsorption syndrome
    • Insulinoma (an insulin-producing tumor)
    • Addison disease (adrenocortical insufficiency)
    • Hypopituitarism (underactivity of the pituitary gland)
    • Hypothyroidism (underactivity of the thyroid gland)

Since the dose of glucose is taken by mouth, the test is sometimes called an oral glucose tolerance test.

Suggested Reading by Our Doctors

• Diabetes - Learn about type 1 and 2 diabetes (Diabetes Mellitus) symptoms including increased urination, thirst, weight loss, fatigue, nausea, vomiting, skin infections, and blurred vision. Causes and diagnosis information is provided in the information.
• Insulin Resistance - Insulin resistance is caused by obesity, pregnancy, stress, metabolic syndrome, and steroid use. It is associated with obesity, fatty liver, type 2 diabetes, heart disease, skin tags, polycystic ovary disease, and growth abnormalities.
• Metabolic Syndrome - Metabolic syndrome risk factors include high blood pressure, obesity, high cholesterol, and insulin resistance. Prevention and treatment include lifestyle changes and medication.

Read more Glucose Tolerance Test related articles »

Latest Medical News

• Glucose Challenge in Pregnancy Could Predict Heart Disease
• Patients Not Always Told of Lab Results
• Diabetes Keeps Rising Among U.S. Adults