Diabetic blood glucose value for a long time in 15mmol / L, belongs to the higher level, easy to cause acute and chronic complications of diabetes, serious cases will be life-threatening. 1. Acute complications: Blood glucose continues to be at a high level, suggesting that the body’s pancreatic islet dysfunction, impaired utilization of glucose, will lead to metabolic disorders, prone to diabetic ketoacidosis, hyperosmolar hyperglycemia, lactic acidosis, etc., which are acute complications of diabetes mellitus, and in serious cases, can be life-threatening. 2. Chronic complications: Diabetic patients with long-term poor glycemic control will have chronic complications, complications include macrovascular lesions, microvascular lesions, neuropathy and so on. (1) Diabetic macrovascular lesions: mainly including lower limb atherosclerosis occlusion, coronary atherosclerosis, cerebral atherosclerosis and so on. (2) Microangiopathy: retinal vasculopathy caused by high blood sugar. Diabetic nephropathy, caused by a decrease in glomerular filtration rate, causing proteinuria, and eventually developing into renal failure. (3) Neuropathy: diabetic neuropathy, mainly for the hands and feet end of the sensory abnormalities, numbness, pain, pins and needles sensory abnormalities. Diabetic hyperglycemia, at first, may not have any symptoms, patients are often easy to pay no attention to the persistent hyperglycemia eventually cause irreversible physical damage. Therefore, once you find elevated blood sugar, go to the hospital in time.