The normal value of glycated hemoglobin in normal people should be within the range of 4.0 to 6.0%, reflecting the patient’s blood sugar control in the past 3 months. Glycated hemoglobin greater than or equal to 6.5% can be used to assist in the diagnosis of diabetes mellitus. Glycated hemoglobin is produced when glucose in the blood combines with hemoglobin in the red blood cells of the blood. Hemoglobin can survive in the blood for about 3 months, therefore, glycated hemoglobin can reflect the average level of glucose in the blood in the past 3 months. The normal value of glycated hemoglobin in a normal person should be in the range of 4.0 to 6.0%. Glycated hemoglobin can be used to assist in the diagnosis of diabetes mellitus, and our guideline suggests that a glycosylated hemoglobin greater than or equal to 6.5% can be used as a reference for the diagnosis of diabetes mellitus in healthcare institutions where conditions are ripe. Glycated hemoglobin can also be used to evaluate the glycemic control of diabetic patients in the last 3 months, therefore, diabetic patients should have their glycated hemoglobin checked every 3 months, and for diabetic patients, the control target of glycated hemoglobin is less than 7%. For patients with higher than normal glycosylated hemoglobin, it is necessary to go to the endocrinology department of the hospital in a timely manner for appropriate examination to evaluate the presence of diabetes or to adjust the glucose-lowering program.