The latest guidelines on glycosylated hemoglobin: After 2010, the American Diabetes Association (ADA) and the World Health Organization (WHO) have approved glycosylated hemoglobin (HbA1c) as one of the diagnostic criteria for diabetes, and the ADA’s 2012 diabetes guidelines on the diagnostic criteria for diabetes mention that the value of glycosylated hemoglobin should be greater than or equal to 6.5%. It is not currently implemented as a diagnostic criterion in China. The principle of glycated hemoglobin: Glycated hemoglobin (HbA1c) is a product of the slow, continuous and irreversible formation of non-enzymatic protein glycation of hemoglobin with glucose in red blood cells. The valine at the amino terminus of the 2 beta chains of hemoglobin combines non-enzymatically with glucose to form Schiff bases, which are rearranged by Amadori to produce ketamine, an irreversible reaction, so HbA1c levels are positively correlated with blood glucose concentrations. Since the life span of erythrocytes in the blood circulation is about 120 days, HbA1c can accurately reflect the total blood glucose level in the last 2-3 months, but the effect of blood glucose concentration on HbA1c level varies in different periods during the life span of erythrocytes, with the effect of blood glucose concentration on HbA1c reaching 50% in 30 days, 40% in 31-90 days, and 91-120 days. The effect of blood glucose concentration on HbA1c level is 50% within 30 days, 40% within 31-90 days, and only 10% within 91-120 days. The significance of glycosylated hemoglobin: The two most authoritative clinical studies on diabetes, the US Diabetes Control and Complications Trial (DCCT) and the UK Prospective Diabetes Study (UKPDS), have established the importance of glycemic control in the treatment of diabetes and established HbA1c as the gold standard for glycemic evaluation. Influencing factors of glycated hemoglobin: The influencing factors of HbA1c include gender, hypertension, fasting glucose, postprandial glucose, islet cell function, high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), triglycerides (TG), and hemoglobin (Hb). Multiple stepwise regression analysis showed that fasting, postprandial glucose, islet cell function, and insulin resistance index had the greatest influence on HbA1c had the greatest effect. Association between glycosylated hemoglobin and coronary heart disease: Some studies have shown that glycosylated hemoglobin levels are significantly higher in diabetes combined with coronary heart disease compared to diabetes alone.