The glucose tolerance signifies the ability of the body to dispose off an additional load of glucose given. This test is useful in distinguishing a person with a normal glucose tolerance from people who have increased tolerance in disease conditions. Aim of the study to study on glucose tolerance test. Approximately 40% of subjects who will develop type 2 diabetes are within the NGT range at OGTT, indicating that there is a large number of NGT subjects who constitute the larger reservoir of future type 2 diabetes. OGTT detects diabetes more efficiently than FPG as it recognizes altered post-prandial metabolism.