High blood sugar is not necessarily diabetes. First of all, the diagnosis of diabetes mellitus refers to the typical symptoms of diabetes mellitus, three more and one less symptom of dry mouth, drinking, urinating and wasting, together with a random blood glucose greater than or equal to 11.1mmol/L. Or fasting blood glucose is greater than or equal to 7.0mmol/L, and the glucose of 2 hours after meal of glucose test of glucose tolerance test is greater than or equal to 11.1mmol/L. If the above three points satisfy two of these three points, the diagnosis can be made. However, each point needs to be confirmed on another day because human blood sugar fluctuates, and a single check of high blood sugar does not diagnose diabetes. There are many other reasons for false elevation of blood glucose, such as physiological reasons, such as overeating, mood changes, cold and hot stimuli, trauma, infections, and surgical procedures and other stressful conditions can cause an increase in blood glucose, but the increase in blood glucose caused by these conditions are usually transient, and when the stress is removed, the blood glucose will naturally return to normal. There are also some drugs, such as diuretics furosemide, hydrochlorothiazide, glucocorticoid prednisone, methylprednisolone, etc., and psychoneurotics such as olanzapine, but high blood glucose caused by drugs and physiological causes of high blood glucose are the same as temporary, and blood glucose can be restored to normal after stopping the drug. There are also liver function damage, pancreatic islet cell tumor, cortisolism and other special diseases can also cause transient blood glucose elevation, blood glucose can be returned to normal after treatment of the disease. Therefore, it is necessary to clarify the degree of blood glucose elevation, clarify the cause of blood glucose elevation, discharge other causes of blood glucose elevation, and the value of blood glucose elevation reaches the diagnostic standard of diabetes before determining that it is diabetes mellitus.