Check diabetes generally need to measure fasting blood glucose, 2 hours postprandial blood glucose, glycated hemoglobin, glucose tolerance test, checking fasting blood glucose and glucose tolerance test is required to fasting, so check diabetes generally need to fasting. 1. Fasting blood glucose: is measured in the fasting state of venous plasma glucose, fasting blood glucose ≥ 7mmol / L and polyuria, polydipsia, polyphagia, weight loss symptoms can be considered diabetes. 2. 2-hour postprandial blood glucose: venous plasma blood glucose is measured 2 hours after a normal diet, 2-hour postprandial blood glucose ≥11.1mmol/L and urination, drinking, eating and weight loss symptoms can be considered diabetes mellitus. 3. Glycated hemoglobin: it can reflect the average blood sugar level in the last 2~3 months, glycated hemoglobin ≥6.5% and symptoms of polyuria, polydipsia, polyphagia, polyphagia and weight loss can be considered as diabetes mellitus. 4. Glucose tolerance test: glucose tolerance test is also an important method to diagnose diabetes. The general method is to measure blood glucose on an empty stomach, and then take 75 grams of anhydrous glucose dissolved in 250-300 ml of water at one time, and measure the blood glucose 0.5, 1, 2, 3 hours after glucose tolerance. Checking for diabetes requires fasting, and the test is completed under the supervision of a doctor.