HbA1c is the fraction of hemoglobin A that is first reversibly, then irreversibly glycated at one or both N-terminal valines of the β-chain.
The longer red blood cells are in circulation and the higher the ambient glucose levels, the higher the concentration of HbA1c. This biology makes HbA1c a good marker for estimation of the average blood glucose levels in the preceding 3 months. The HbA1c assay is useful in the:
- diagnosis of diabetes mellitus,
- identification of patients at risk for developing diabetes, and
- monitoring of patients with diabetes mellitus.
For monitoring diabetic patients, it is recommended that glycemic goals are individualized following current professional society recommendations. As recommended by the American Diabetes Association (ADA), patients in the range of 5.7 to 6.4% HbA1c (39 to 46 mmol/mol) would be in the category of increased risk for diabetes and results ≥ 6.5% (48 mmol/mol) may aid in the diagnosis of diabetes.