HbA1c

HbA1c is a modified form of haemoglobin. Haemoglobin is the molecule in our red blood cells which carries oxygen around the body; most of the haemoglobin is of a type called HbA. A small fraction of HbA becomes modified during its lifetime (HbA1). In the late 1950s it was found that HbA1 could be separated further into HbA1a, HbA1b and HbA1c. A decade later, the clinical significance of HbA1c became apparent when it was revealed that many diabetics had uncharacteristically high levels of this haemoglobin variant.

HbA1c is formed when glucose molecules attach to HbA molecules in a process known as glycosylation. Glycosylation reactions are common and occur naturally in the body. Normally though, they take place in a controlled environment, regulated by enzymes. The process by which HbA1c is formed, however, occurs in the absence of enzymes and is therefore referred to as non-enzymatic glycosylation, or simply 'glycation'.