In general, glycated hemoglobin reflects the patient’s blood glucose level for the previous 2-3 months. Glycosylated hemoglobin, i.e. non-enzymatic glycosylation of hemoglobin, is produced by the combination of blood sugar and hemoglobin, which is an irreversible reaction and is proportional to blood sugar concentration, and can be maintained in the blood for 2-3 months, and can reflect the blood sugar level of the patient in the previous 2-3 months. Blood glucose is the monosaccharide of carbohydrate decomposition in blood. Fasting blood glucose and 2-hour postprandial blood glucose are the measurement of patients’ immediate blood glucose, which is the standard for diagnosing diabetes. Glycosylated hemoglobin, on the other hand, does not diagnose diabetes, but it can monitor the level of blood glucose control of diabetic patients in the past 2-3 months and make adjustments to the patient’s treatment. If glycosylated hemoglobin is high, you should promptly control the diet in daily life, limit the daily sugar intake, and try to eat less fruits with more sugar.