Review of hemoglobin A(1c) in the management of diabetes

J Diabetes. 2009 Mar;1(1):9-17. doi: 10.1111/j.1753-0407.2009.00009.x. Epub 2009 Jan 27.


Hemoglobin HbA(1c) (A(1c)) has been used clinically since the 1980s as a test of glycemic control in individuals with diabetes. The Diabetes Control and Complications Trial (DCCT) demonstrated that tight glycemic control, quantified by lower blood glucose and A(1c) levels, reduced the risk of the development of complications from diabetes. Subsequently, standardization of A(1c) measurement was introduced in different countries to ensure accuracy in A(1c) results. Recently, the International Federation of Clinical Chemists (IFCC) introduced a more precise measurement of A(1c) , which has gained international acceptance. However, if the IFCC A(1c) result is expressed as a percentage, it is lower than the current DCCT-aligned A(1c) result, which may lead to confusion and deterioration in diabetic control. Alternative methods of reporting have been proposed, including A(1c) -derived average glucose (ADAG), which derives an average glucose from the A(1c) result. Herein, we review A(1c) , the components involved in A(1c) formation, and the interindividual and assay variations that can lead to differences in A(1c) results, despite comparable glycemic control. We discuss the proposed introduction of ADAG as a surrogate for A(1c) reporting, review imprecisions that may result, and suggest alternative clinical approaches.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Biomarkers / blood
  • Blood Chemical Analysis / standards
  • Blood Glucose / drug effects
  • Blood Glucose / metabolism
  • Diabetes Mellitus / blood
  • Diabetes Mellitus / drug therapy*
  • Glycated Hemoglobin / metabolism*
  • Humans
  • Hypoglycemic Agents / therapeutic use*
  • Predictive Value of Tests
  • Reproducibility of Results
  • Treatment Outcome


  • Biomarkers
  • Blood Glucose
  • Glycated Hemoglobin A
  • Hypoglycemic Agents
  • hemoglobin A1c protein, human