Glycated hemoglobin

Glycated hemoglobin, glycohemoglobin, glycosylated hemoglobin is a form of hemoglobin (Hb) that is chemically linked to a sugar. Several types of glycated hemoglobin measures exist, of which HbA1c, or simply A1c, is a standard single test.^[1] Most monosaccharides, including glucose, galactose, and fructose, spontaneously (i.e. non-enzymatically) bond with hemoglobin when present in the bloodstream. However, glucose is only 21% as likely to do so as galactose and 13% as likely to do so as fructose, which may explain why glucose is used as the primary metabolic fuel in humans.^[2][3]

The excess formation of the sugar-hemoglobin linkage indicates the presence of excessive sugar in the bloodstream, and is an indicator of diabetes or other hormone diseases in high concentration (HbA1c >6.4%).^[4] A1c is of particular interest because it is easy to detect. The process by which sugars attach to hemoglobin is called glycation and the reference system is based on HbA1c, defined as beta-N-1-deoxy fructosyl hemoglobin as component.^[5]

HbA1c is measured primarily to determine the three-month average blood sugar level and is used as a standard diagnostic test for evaluating the risk of complications of diabetes and as an assessment of glycemic control.^[1][6] The test is considered a three-month average because the average lifespan of a red blood cell is three to four months. 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. In diabetes, higher amounts of glycated hemoglobin, indicating higher of blood glucose levels, have been associated with cardiovascular disease, nephropathy, neuropathy, and retinopathy.