A blood test that determines the amount of glucose in the blood after an overnight fast of at least 8 hours; a measure at or above 126 mg/dL indicates diabetes.

The preferred method of screening for diabetes. The FPG measures a person's blood glucose level after fasting or not eating anything for atleast 8 hours. Normal fasting blood glucose is less than 100 milligrams per deciliter or mg/dL. A fasting plasma glucose greater than 100 mg/dL and less than126 mg/dL implies that the person has an impaired fasting glucose level, but may not have diabetes. A diagnosis of diabetes is made when the fasting blood glucose is greater than 126 mg/dL and when blood tests confirm abnormal results. These tests can be repeated on a subsequent day or by measuring glucose 2 hours after a meal. The results should show an elevated blood glucose of more than 200 mg/dL.

A diagnostic test for diabetes, performed after the patient has had nothing to eat or drink overnight.