The fasting plasma glucose test is performed after a person has fasted for at least 8 hours. A sample of blood is taken from a vein in the arm. If the blood glucose level is greater than or equal to 126 mg/dl, the person is retested and, if the results are consistent, diagnosed with diabetes. (Until recently, the diagnostic cut-off point was 140 mg/dl, but the ADA lowered it because research has shown that even people with fasting plasma glucose levels between 126 mg/dl and 140 mg/dl tend to develop the medical complications of diabetes.)