HbA1c (NGSP)
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 live for months, it reflects average blood glucose over the past few months. The NGSP version expresses the result as a proportion of total hemoglobin, in units standardised by the National Glycohemoglobin Standardization Program.
It is the same measurement as HbA1c (IFCC), shown in different units, and reports often print both. It is read with Glucose, with an estimated average glucose value calculated from it, and sometimes with Fructosamine, which reflects a shorter window.
No fasting is needed. Conditions that change red cell lifespan, such as blood loss, anemia or a recent transfusion, can move the result, and some hemoglobin variants interfere with certain assays. HPLC methods can often detect these variants. Labs may print it as HEMOGLOBIN A1c or Hemoglobina A1c (NGSP) por HPLC.
Reference ranges labs publish
Each lab states an interval for its own method and the population it measured. They differ, they are not interchangeable, and none of them is a verdict on a single result.
- Everyone (not split by sex or age): 4 to 5.6 % · Ion-exchange HPLC · Source: Mayo Clinic Laboratories, HBA1C (Hemoglobin A1c, Blood) (read 2026-09-24)
- Everyone (not split by sex or age): 4.8 to 5.6 % · Immunoturbidimetric (Roche Tina-quant) · Source: Labcorp, 001453 (Hemoglobin (Hb) A1c) (read 2026-09-24)
Often read alongside: HbA1c (IFCC), Glucose, Estimated average glucose (mg/dL), Fructosamine, Hemoglobin