<P> Glycated hemoglobin (hemoglobin A1c, HbA, A1C, or Hb; sometimes also referred to as being Hb1c or HGBA1C) is a form of hemoglobin that is measured primarily to identify the three - month average plasma glucose concentration . The test is limited to a three - month average because the lifespan of a red blood cell is four months (120 days). However, since red blood cells do not all undergo lysis at the same time, HbA1C is taken as a limited measure of three months . It is formed in a non-enzymatic glycation pathway by hemoglobin's exposure to plasma glucose . </P> <P> HbA is a measure of the beta - N - 1 - deoxy fructosyl component of hemoglobin . The origin of the naming derives from Hemoglobin type A being separated on cation exchange chromatography . The first fraction to separate, probably considered to be pure Hemoglobin A, was designated HbA, the following fractions were designated HbA, HbA, and HbA, respective of their order of elution . There have subsequently been many more sub fractions as separation techniques have improved . Normal levels of glucose produce a normal amount of glycated hemoglobin . As the average amount of plasma glucose increases, the fraction of glycated hemoglobin increases in a predictable way . This serves as an indicator that blood sugar is increasing and that action should be taken . </P> <P> In diabetes mellitus, higher amounts of glycated hemoglobin, indicating poorer control of blood glucose levels, have been associated with cardiovascular disease, nephropathy, neuropathy, and retinopathy . A trial on a group of patients with Type 1 diabetes found that monitoring by caregivers of HbA led to changes in diabetes treatment and improvement of metabolic control compared to monitoring only of blood or urine glucose . However, a trial designed specifically to determine whether reducing HbA below the normal 6%, using primarily insulin and sulfonylureas (both known to easily drive blood sugar too low), would reduce the rate of cardiovascular events in type 2 diabetes found higher mortality--the trial was terminated early . The negative outcomes may well have been a result of the treatment approach, primarily insulin and sulfonylureas, utilized in the "intensive" treatment group instead of LCHF (Low - Carbohydrate High Fat diet), GlP - 1 analogues & SGLT - 2 inhibitors, none of which have these problems & lower cardiovascular mortality . </P> <P> Hemoglobin A1c was first separated from other forms of hemoglobin by Huisman and Meyering in 1958 using a chromatographic column . It was first characterized as a glycoprotein by Bookchin and Gallop in 1968 . Its increase in diabetes was first described in 1969 by Samuel Rahbar et al . The reactions leading to its formation were characterized by Bunn and his coworkers in 1975 . </P>

Glycosylated haemoglobin (hb a1c) level drawn