Glucose measurement is the determination of the amount of glucose in blood plasma. Venous glucose level is the main basis for diagnosing diabetes or abnormal glucose tolerance or impaired fasting glucose regulation. According to the “Chinese guidelines for the prevention and treatment of type 2 diabetes”, normal blood glucose is defined as fasting blood glucose (FBG) <6.1 mmol/L (110 mg/dl) and 2 hours postprandial blood glucose (2hPBG) <7.8 mmol/L (140 mg/dl). The diagnostic criteria for diabetes mellitus are: ① diabetic symptoms (typical symptoms include polyhydramnios, polyuria and unexplained weight loss) plus random blood glucose >= 11.1 mmol/L (200mg/dl), random blood glucose is defined as blood glucose at any time of the day without regard to the time of the last meal; ② FBG >= 7.0 mmol/L (126mg/dl). Fasting state means no calorie intake for at least 8 hours; ③75g glucose load 2 hours blood glucose >=11.1 mmol/L (200mg/dl).