HbA1

HbA1 is a historical term used to describe a collective group of glycated forms of adult hemoglobin (HbA) created when glucose non-enzymatically bonds to the amino termini of globin chains. The term encompasses three major glycation products known as HbA1a, HbA1b, and HbA1c. HbA1c is the best characterized member and is widely used in modern medicine as a marker of long-term glycemic exposure; the A1a and A1b forms are related metabolites that arise through similar non-enzymatic reactions.

Formation of HbA1 variants occurs through the Maillard-type glycation process, which increases with higher blood glucose concentrations. Because red blood cells carry hemoglobin for about 120 days, the amount of HbA1 glycated forms reflects average blood glucose over several weeks to months. HbA1 measurements can be influenced by factors such as age, anemia, hemoglobin variants, and red cell turnover, which can alter interpretation.

In clinical practice, HbA1c is the primary and most widely used measure associated with the HbA1 family for assessing long-term glycemic control in diabetes management. HbA1 and its subforms were historically used in research and certain analytical contexts, but the nomenclature has largely given way to HbA1c as the standard biomarker. Modern laboratories typically report HbA1c values and, less commonly, may discuss the presence of other HbA1 glycated fractions in specialized assays.

See also: HbA1c, glycated hemoglobin, Maillard reaction.