Test, glucose tolerance (GTT)

After fasting, a specific amount (100 grams) of glucose is given by mouth, and the blood levels of this sugar are measured every hour. Normally, the blood glucose should return to normal within 2 to 2 ½ hours. The GTT is considered a classic test of carbohydrate metabolism. It is much used in the diagnosis of diabetes. The GTT 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, and the amount of "active" insulin.