HbA1c is currently the most commonly checked indicator for clinical testing of glycated hemoglobin, and its normal value is generally 4%~6%. Due to the different testing methods and reagents, the reference indexes are different in different hospitals, so it is recommended to consult with your doctor. HbA1c level depends on the blood glucose level and the duration of hyperglycemia, and its production is directly proportional to the blood glucose concentration. Its level reflects the average blood glucose level in the last 2 to 3 months, but does not provide the daily dynamic change of blood glucose or the frequency of abnormal hypoglycemia. Patients with diabetes mellitus should routinely and regularly test HbA₁c at least twice a year, or once every 3 months if glycemic control is poor or treatment regimens are adjusted. HbA1c testing can be used to screen and assess the degree of diabetes control. Patients with abnormal glycosylated hemoglobin are advised to seek prompt medical attention.