A 68-year-old woman comes to the office for a routine physical examination. The patient is asymptomatic but overweight. She has a strong family history of diabetes mellitus. Currently she takes Amlodipine 5 mg. Results of physical examination are normal, except for a BMI of 30. Results of routine laboratory studies show a fasting plasma glucose level of 170 mg／dL. 1 week later, repeated fasting plasma glucose level is 150 mg／dL.