HbA1c - AntiDiabeticMeds

Haemoglobin is a protein responsible for oxygen transport to cells in the body and gives the blood the red colour. Approximately 97% of all haemoglobin consists of haemoglobin A (A=adult). About 3% of the haemoglobin are minor subgroups where A1c is one of these (1, 2). The more glucose in the body the more haemoglobin gets glycated. An HbA1c test is a measure of the percentage of the haemoglobin in the red blood cells that has glucose bound to it, glycated haemoglobin A1c = HbA1c. There is an individual variation how much glucose that is bound to haemoglobin, the number of red blood cells and lifespan. As an average they live 120 days which is the reason an HbA1c test reflect average blood glucose ~6-8 weeks. An HbA1c test is an important tool for diagnose, as follow up for all forms of diabetes and for the right treatment as well. An HbA1c test doesn´t tell us all though, i.e. it doesn´t show frequency of episodes of hypo- and hyperglycaemia.

Some people have higher HbA1c readings due to deficiency of Vitamin B12 or folate, and some have lower readings than normal due to sickle cell disease, haemolytic anemia etc. There is also a relation between HbA1c and ethnicity, some drugs (iron, erythropoietin etc) than might impact the HbA1c reading. Important to know is that if any influence, the impact of these factors is small though. According to WHO (3) a non-diabetic has a A1c below 6% (42 mmol/mol) and according to ADA 5.7% (39 mmol/mol).

The most used standards of measuring HbA1c available in the World today are IFCC, NGSP/DCCT and JDS/JSCC. NGSP/DCCT, JDS/JSCC and the old standard in Sweden, Mono-S, measures in percent how much of the haemoglobin which is glycosylated, using different calibration methods. For IFCC, HbA1c is defined as mmol glycated hexapeptide per mol (glycated and nonglycated hexapeptides): HbA1c/(HbAo + HbA1c), 4.

To convert an HbA1c between different standards, see HbA1c converter.

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