A glucose tolerance test measures the ability of a patient to process glucose in their diet. It is simple in concept but requires a strict protocol in order to give useful results. * The patient's blood sugar level is measured prior to the test; * The patient is then given a fixed amount of glucose solution to drink; * The patient's blood is drawn at regular intervals thereafter and the blood sugar is measured at each point. The patient will not be allowed any further food until the protocol is completed.