Glycated haemoglobin for diagnosis

Early and accurate diagnosis of diabetes ensures effective management and reduces the risk of diabetes-associated complications.1,2

Currently the recommended method for the diagnosis of diabetes is a fasting blood glucose test followed by an oral glucose tolerance test, if required.3,4 Accurately measuring blood glucose levels of has various practical issues. For example, preparation for an oral glucose tolerance test requires a 3-day preparatory diet , overnight fasting and a 2-hour testing period. The consumption of the glucose load is also problematic.2

Using a HbA1c test may overcome many of the practical issues that affect the blood glucose tests.2 HbA1c measures chronic glycaemia rather than immediate (on examination) blood glucose levels.2 The test can be performed at any time of the day and does not require special preparation.2

Using HbA1c in diagnosis

  • HbA1c test should not be used as a screening tool
  • Initial screening of people should be performed using the AUSDRISK tool
  • An HbA1c level ≥ 6.5% (48 mmol/mol) is recommended as the cut off for diagnosing diabetes
  • The test should be repeated in asymptomatic people
  • Test accuracy is effected by conditions that affect red blood cell survival time such as haemolytic anaemia, chronic kidney failure, vitamin B12 and folic acid deficiencies
  • This test is currently not subsidised for diagnosis

HbA1c should not be used for diagnosis in5

  • Children and young people
  • Women who are currently pregnant or have been pregnant in the past 2 months
  • People with suspected type 1 diabetes
  • People with short duration of diabetic symptoms
  • People at high risk of diabetes who are acutely ill
  • People taking drugs that may cause a rapid rise in glucose, such as corticosteroids or antipsychotic drugs (≤ 2 months)
  • People with acute pancreatic damage or who have undergone pancreatic surgery
  • People with kidney failure
  • People with HIV infection


  1. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). UK Prospective Diabetes Study (UKPDS) Group. Lancet 1998;352:837–53. [PubMed]
  2. d'Emden MC, Shaw JE, Colman PG, et al. The role of HbA1c in the diagnosis of diabetes mellitus in Australia. Med J Aust 2012;197:220–1. [PubMed]
  3. Diabetes Australia. Diabetes management in general practice. Diabetes Australia and The Royal Australian College of General Practitioners, 2012. (accessed 22 January 2013).
  4. Guidelines for preventive activities in general practice (The Red Book) 8th Edition. Melbourne: The Royal Australian College of General Practitioners, 2012. (accessed 8 January 2013).
  5. Farmer A. Use of HbA1c in the diagnosis of diabetes. BMJ 2012;345:e7293. [PubMed]