HbA1c (IFCC)
What it measures, and what changes the number.
HbA1c is the fraction of hemoglobin in red blood cells that has glucose attached to it. Because red cells circulate for months, it reflects average blood glucose over the past few months rather than at a single moment. The IFCC version reports this in mmol/mol, based on a reference method from the International Federation of Clinical Chemistry.
It is the same measurement as HbA1c (NGSP), just expressed in different units, and many reports show both. It is read with Glucose, with an estimated average glucose value derived from it, and sometimes with Fructosamine, which covers a shorter period.
Fasting is not required. Anything that changes red cell lifespan, such as blood loss, anemia or recent transfusion, can shift the result, and some hemoglobin variants interfere with certain methods. HPLC methods can often flag such variants. Labs may print it as Hemoglobina A1c (IFCC) por HPLC.
Often read alongside: HbA1c (NGSP), Glucose, Estimated average glucose (mmol/L), Fructosamine, Hemoglobin