When - Within 1 day. Most commonly used to diagnose gestational diabetes. Also used to diagnose diabetes in people who exhibit symptoms but have high-normal results on blood glucose test. How it works - The pancreas releases insulin into the bloodstream to regulate the body's processing of glucose. By measuring the amount of glucose in the blood after a concentrated amount of glucose is ingested, it is possible to assess how well insulin is functioning.
Preparation Eat and exercise normally for three days prior to the test.
Be sure to consume sufficient carbohydrates. Take nothing but water for ten hours before the test. Avoid smoking before the test. Bring reading material or something else to keep you occupied between blood drawings. An initial fasting blood sample is drawn from a vein in your arm.