Diabetes is a chronic metabolic disease that is dominated by elevated blood glucose. Poor long-term blood glucose control in diabetic patients can produce a variety of complications in the heart, brain, kidney, nerves, and fundus. Complications can occur even when blood glucose is well controlled, because elevated blood glucose is an important but not the only cause of diabetes complications. In addition to elevated blood glucose, there are other causes that can lead to or aggravate the occurrence and development of complications, mainly the following: First, the magnitude of blood glucose fluctuations, the generation of complications is related to the degree of diabetes control, but also with the magnitude of blood glucose fluctuations, the duration of diabetes. Blood glucose fluctuation is obvious and the duration of the disease is long to produce various complications. Second, lifestyle, smoking, alcohol consumption, exercise and other lifestyle affect the occurrence and development of diabetes complications. Third, the presence of metabolic diseases such as obesity, hypertension, hyperlipidemia and hyperuricemia can also aggravate the occurrence and development of diabetic complications. Fourth, disorders of other endocrine hormone levels. Elevated blood glucose is the prominent manifestation of diabetes, and behind the elevated blood glucose there are abnormalities of insulin levels, glucagon, glucocorticoids and abnormalities of catecholamines and inflammatory mediators, all of which can affect the generation and development of diabetic complications. Therefore, even if the blood sugar of diabetic patients is well controlled, complications can arise.