Diabetes is a chronic disease that often does not cause much inconvenience to the patient as far as the disease itself is concerned, and many develop the disease unknowingly. Therefore, many patients do not take it seriously even if they know they have diabetes, and do not pay attention to the necessary tests and proper treatment. In fact, diabetes is a “silent killer”, and poor long-term blood sugar control will cause the real danger of diabetes – acute and chronic complications of diabetes. Acute complications can be life-threatening in severe cases, and chronic complications can be disabling in severe cases. So when complications occur, it is too late to regret them. Acute complications of diabetes include diabetic ketoacidosis, diabetic hyperosmolar state and lactic acidosis, etc. Hypoglycemia is also one of the most common and serious acute complications. Lactic acidosis is a serious acute complication in type 2 diabetic patients taking high doses of biguanide hypoglycemic drugs, especially taking phenylephrine (hypoglycemia), with a low incidence, but once it occurs, the morbidity and mortality rate is high. After the widespread use of insulin, the number of patients dying from acute complications of diabetes such as ketoacidosis and diabetic hyperosmolar state has decreased significantly. Chronic complications of diabetes include diabetic eye disease, diabetic nephropathy, peripheral vascular disease, peripheral neuropathy, diabetic foot and skin lesions. Chronic complications are the result of poor long-term glycemic control and are the main cause of disability and reduced quality of life in patients with diabetes. Many clinical studies have proved that if patients can effectively control their blood glucose for a long time, the occurrence and development of chronic complications can be stopped or delayed.