Fasting blood sugar 12.5mmol/L is more serious. The normal value of fasting blood glucose is usually 3.9~6.1mmol/L. Fasting blood glucose 12.5mmol/L has reached the diagnostic standard of diabetes mellitus, so fasting blood glucose 12.5mmol/L is more serious. The patient’s fasting blood sugar has reached 12.5mmol/L, should immediately go to the hospital, under the guidance of the doctor through the fasting blood glucose test, two hours after meal blood glucose, glycated hemoglobin and other tests on the patient’s blood glucose status to have an understanding. If the patient did not have diabetes before, it needs to be correctly diagnosed and treated by the doctor according to the patient’s condition; if the patient is a diabetic, it means that the patient’s blood glucose control is poor, and the treatment program should be adjusted, and insulin hypoglycemic treatment can be carried out under the guidance of the doctor. If the patient test found fasting blood glucose 12.5mmol/L, need to actively cooperate with the doctor’s treatment, blood glucose control within a reasonable range.