If a diabetic patient has a prolonged fasting blood glucose of 8.9mmol/L may increase the risk of diabetic complications, which is more dangerous, and it is recommended to consult a doctor in time. Diabetic patients fasting blood glucose control target is between 4.4~7.0mmol/L, elderly diabetic patients can appropriately relax the standard of fasting blood glucose, but fasting blood glucose 8.9mmol/L still belongs to the high, appear fasting blood glucose 8.9mmol/L need to pay attention to the daily diet and take medication on time, daily life to strengthen the control of fasting blood glucose. If the long-term fasting blood glucose is 8.9mmol/L, it means that the fasting blood glucose is not well controlled for a long time, which may induce diabetic cardiovascular disease, diabetic nephropathy, diabetic retinopathy and other serious complications, which are more serious. Patients diagnosed with diabetes mellitus should actively cooperate with the doctor’s treatment, strengthen dietary control, moderate exercise, blood sugar control within a reasonable range.