The harm of hyperglycemia. Short-term, one-off hyperglycemia is not serious harm to human body. For example, in a state of tension or emotional excitement and high tension, transient hyperglycemia may occur; Eating a lot of sugar at a time can also lead to short-term hyperglycemia; Subsequently, the blood sugar level gradually returned to normal. However, long-term hyperglycemia will cause pathological changes in all tissues and organs of the whole body, leading to acute and chronic complications. Such as pancreatic failure, water loss, electrolyte disorder, nutritional deficiency, decreased resistance, impaired renal function, neuropathy and fundus lesions.