Glucose tolerance test: A test of carbohydrate metabolism that is used primarily in the diagnosis of type II?diabetes?and?gestational diabetes. Abbreviated GTT. After the patient has fasted overnight, but before breakfast, a specific amount of?glucose?is given by mouth, and the blood levels of this sugar are measured at intervals. The GTT result depends on a number of factors, including the ability of the intestines 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.
