Oral Glucose Tolerance Test

It is one of the methods used in type 2 diabetes screening.

METHODOLOGY

• Administer 75 g of glucose dissolved in 300 ml of water, to be consumed within no more than 3 minutes; in children, use 1.75g/body kg, without exceeding 75g.
• Venous blood is sampled prior to the administration of the glucose and 2 hours afterwards. For the diabetes diagnosis, the 2-hour interval is sufficient (according to WHO).
• The glucose levels in the whole venous blood are generally lower than in the venous plasma, for the same volume unit (because red blood cells contain a small quantity of glucose), and the glucose level in the capillary blood is higher than in the venous blood (a part of the glucose is extracted at the level of the capillaries);
• Under special circumstances, the determinations may be performed over up to 5 hours (tardy pancreas response). For instance, in order to diagnose reactive hypoglycemia, a test that expands over 3, 4, 5 hours is recommended.