Oral glucose tolerance test (OGTI) is a test done to determine how the body handles the sugar or glucose from the food that is consumed. This test can determine whether a person is at a risk of developing Diabetes or already have it. OGTT is one of the confirmatory tests done to diagnose Type 2 Diabetes and Gestational Diabetes Mellitus (GDM) which is diagnosed at 24-28 weeks of pregnancy. .Test explainedThe test is done after 8 hours of fasting. After the blood is drawn to test fasting blood sugar, the individual is given 75 g of glucose, mixed in water, orally and then blood is drawn again after 2 hours to test post-prandial blood glucose.Individuals who are obese, with family history of Diabetes, elevated triglycerides and with fasting blood sugar above 100 mg/dL are recommended OGTI. Women with polycystic ovarian syndrome (PCOS), women who have delivered large babies (birth weight > 4 kg) and women with GDM in the last pregnancy are also recommended OGTI. Individuals with anaemia may be recommended OGTT to diagnose Diabetes.Performing the Testlndividual undergoing this test should not be taking medicines which would alter the blood sugar level. Also, they should not be ill,not even common cold. The blood is drawn from the vein of the arm after 8 to 12 hours of fasting. 75 g of anhydrous glucose is mixed in water and consumed by the individuals undergoing the test. This is followed again by another blood drawn from the arm after 2 hours of consumption of 75 g of glucose.As with any blood draw, it may be difficult to find vein, hence blood may not be drawn in the first prick. Mild bleeding, bruising, pain at the site of blood draw, are a few side effects of the test.The indMdual needs to stay close to the lab, as the blood needs to be re-drawn in fasting and 2 hours after consumption of 75 g of glucose. Hence other than 3-hour absence from daily routine, no major difficulty is faced by the individual undergoing the test.Test InterpretationPrediabetes is defined as a condition, where in the blood sugar values are not normal however not high enough to satisfy the criteria for Diabetes diagnosis. If the fasting blood sugars are higher than 100 mg/dL but lower than 126 mg/dL, it is defined as impaired fasting glucose. If 2 hour post-prandial blood sugars are higher than 140 mg/dL but lower than 200 mg/dL then it is defined as impaired glucose tolerance. Both impaired fasting blood glucose and impaired glucose tolerance belong to Prediabetes category.People diagnosed with prediabetes are at risk of developing Diabetes in 5 to 10 years, if they don't follow a healthy lifestyle with a balanced, healthy diet and physical exercise. Research studies have shown that losing 5 per cent of the body weight can reverse prediabetes. Sometimes 3-hour OGTI is performed in pregnancy. Here instead of 75 g of oral glucose, 100 g of glucose is consumed.Dr Suganthi Kumaran is a Consultant Physician.