A fasting blood glucose 8.4mmol / L, need to further improve the glucose tolerance test, glycated hemoglobin, etc. to understand whether there is diabetes. If it is type 2 diabetes mellitus, you can usually follow the doctor’s advice to choose bisphosphonates, sulfonylureas, glinides, thiazolidinediones, etc.; if it is type 1 diabetes mellitus, you need insulin therapy. After diagnosed with diabetes, patients with type 2 diabetes can choose the following drugs, such as: metformin hypoglycemic effect is significant, there is a weight loss effect, the risk of hypoglycemia is small. Sulfonylureas and glinides are insulinotropic agents that bring down blood sugar. Thiazolidinediones such as rosiglitazone increase the sensitivity of target tissues to insulin action and reduce blood glucose. There are also alpha-glucosidase inhibitors and others. Lifelong insulin therapy is required for type 1 diabetes mellitus, including insulin menthyl and glycemic insulin, etc. Type 2 diabetes mellitus is also required when glycemic control is not achieved despite lifestyle interventions and combination therapy with larger doses of multiple oral hypoglycemic agents. Fasting blood glucose 8.4mmol / L in addition to drug therapy, but also combined diet and exercise therapy. Diet, we should strictly control the daily energy intake, small meals, low-salt, low-fat, low-sugar diet; exercise, you should adhere to the exercise, aerobic exercise, such as swimming, jogging, yoga and so on. Fasting blood glucose 8.4mmol / L should go to the hospital, under the guidance of the doctor treatment, do not take their own medication, pay attention to avoid the contraindication of the drug crowd, while preventing adverse drug reactions.