Diabetes mellitus is a chronic metabolic disease, and the danger of diabetes mellitus is that it is prone to a variety of acute and chronic complications. When fasting blood sugar reaches about 23mmol/L, the following dangers may occur: i. Diabetic patients are prone to diabetic ketosis or even diabetic ketoacidosis when their blood sugar is greater than 16.9mmol/L. Diabetic ketoacidosis is an acute complication of diabetes that endangers patients’ lives. Second, when fasting blood sugar reaches about 23mmol/L, it is also easy to complicate hyperosmolar coma, which is also an acute complication of diabetes, and the mortality rate of hyperosmolar coma is higher than that of ketoacidosis, which requires active rescue and treatment. Third, if the fasting blood sugar is too high for a long time, in addition to various acute complications, it is also easy to complicate chronic complications such as heart, brain, kidney and fundus, such as coronary heart disease, angina pectoris, myocardial infarction, cerebral infarction, diabetic nephropathy and cardiac insufficiency.