The postprandial blood sugar determines the glucose concentration 2 hours after having breakfast/ lunch. Blood sugar levels usually begin to rise 10-15 minutes after a meal and reach their peak after an hour. The pancreas produces the hormone insulin, which aids in the absorption of sugar from the bloodstream into the body cells. This test is used to assess how the body reacts to sugar and starch after eating a meal. Doctors recommend this test if your blood sugar continues to be excessively high or extremely low. Blood sugar levels in people who do not have diabetes normally return to normal within 2 hours.