HbA1c: how do we measure it and what does it mean?

Curr Opin Endocrinol Diabetes Obes. 2009 Apr;16(2):113-8. doi: 10.1097/MED.0b013e328327728d.


Purpose of review: Description of recent developments in the standardization of HbA1c measurement and interpretation of HbA1c results.

Recent findings: HbA1c is extensively used in the management of patients with diabetes. The two major schemes to standardize HbA1c produce values that differ substantially. A prospective, multinational study revealed a linear correlation between HbA1c and average blood glucose. Some, but not all, assay methods are able to accurately measure HbA1c in individuals with common hemoglobin variants.

Summary: Progress in standardization of methods for HbA1c measurement has significantly reduced variation among different methods. The improved accuracy could allow HbA1c to be used for screening and diagnosis of diabetes. A consensus document recommends that HbA1c be reported in both NGSP (%) and IFCC (mmol/mol) units. HbA1c results can be translated into estimated average glucose (eAG), which could be reported in addition to HbA1c.

Publication types

  • Review

MeSH terms

  • Diabetes Mellitus / blood
  • Diabetes Mellitus / diagnosis
  • Glucose / metabolism
  • Glycated Hemoglobin A / analysis*
  • Glycated Hemoglobin A / physiology*
  • Hemoglobins / metabolism
  • Humans
  • Reference Values


  • Glycated Hemoglobin A
  • Hemoglobins
  • Glucose