High blood glucose in diabetes can be serious, and poor blood glucose control may lead to acute and chronic complications of diabetes, which can be serious and life threatening. Diabetes mellitus is a metabolic disease characterized by chronic elevation of blood glucose due to multiple causes. Prolonged hyperglycemia may damage several body systems, such as the cardiovascular system, nervous system, and urinary system. High blood glucose may lead to acute complications of diabetes, including diabetic ketoacidosis and diabetic hyperosmolar hyperglycemic coma, resulting in severe metabolic disorders in the body, which are critical and life-threatening. High blood glucose can lead to decreased immunity, easy to get infected, and the infection is not easy to control, serious cases can lead to infectious shock or even life-threatening. High blood sugar can involve the cardiovascular system, leading to coronary heart disease, diabetic cardiomyopathy, heart failure, etc.; high blood sugar can involve the urinary system, leading to nephropathy, renal failure. High blood glucose should be found in a timely manner to consult a doctor, follow the doctor’s instructions to control blood glucose, to prevent or delay the occurrence of complications.