4363.0.55.001 - Australian Health Survey: Users' Guide, 2011-13  
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 11/12/2013   
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Contents >> Biomedical Measures >> Diabetes biomarkers >> Glycated haemoglobin (HbA1c)



The body converts blood sugar into energy in the body by a hormone called insulin. However, people with diabetes do not produce sufficient insulin, therefore blood sugar is not converted into energy, which causes high blood sugar levels (glycemia).

In previous years fasting plasma glucose has been the measurement of choice for diagnosing diabetes, however these levels fluctuate from day to day. Glycated haemoglobin (HbA1c) on the other hand has recently been endorsed by WHO as the measurement of choice for the diagnosis of diabetes.1 HbA1c, in simple terms, is haemoglobin which is bound to a glucose particle in the blood for the average life span of a red blood cell (around 120 days). HbA1c levels generally reflect the average blood glucose over three months.

The HbA1c test measures the amount of glucose circulating in the blood that binds to the haemoglobin present in red blood cells, forming HbA1c. Mature red blood cells live for approximately three months within the blood circulation, which enables this test to measure chronic (long term) glycemia.


HbA1c test results were obtained for persons aged 12 years and over, who agreed to participate in the National Health Measures Survey (NHMS) and provided a blood sample. Fasting was not required for this test.


A blood sample was collected from participants and HbA1c (%) levels were measured at the Douglass Hanly Moir (DHM) laboratory.

In the NHMS, cut off reference values for normal and abnormal results were sourced from World Health Organization (WHO) guidelines1 and the position statement for diagnosing diabetes in Australia.2 These guidelines are based on epidemiological data and publications of major clinical trials.

HbA1c units of measurement were reported in the NHMS using both the National Glycohemoglobin Standardization Program (NGSP) units (percentage) and the Système International (SI) units (mmol/mol) as recommended by the International HbA1c Consensus Committee.3 In the NHMS, the following equation was used to convert the HbA1c units of measurement from percentage to mmol/mol, as described in the Diabetes Australia guidelines.4

HbA1c SI unit (mmol/mol) = 20 + 11 (A1c% - 4)

Alternatively, the below equation can also be used to convert results between the two units, as described in the Medical Journal of Australia: 3

HbA1c SI unit (mmol/mol) = 10.93 × HbA1c NGSP unit (%) − 23.50

In the NHMS, the following definitions were used for whole blood HbA1c:

Cut off points for HbA1c in the NHMS

HbA1c levels
HbA1c levels

Has diabetes (Abnormal)≥6.5≥48
At high risk of diabetes6.0 to <6.542 to <48
No diabetes (Normal)<6.0<42

In the NHMS, the HbA1c results, in addition to the self reported data on diabetes were used to estimate the prevalence of diabetes and information on diabetes management in Australia. Information about the definitions for measuring diabetes is available from the Diabetes biomarkers topic page of this chapter.

Further test information about the analysis method and machine used to measure HbA1c levels is available in Excel spreadsheet format in the Downloads page of this product.

Data items

The data items and related output categories for this topic are available in Excel spreadsheet format from the Downloads page of this product.


Points to be considered when interpreting data for this topic include the following:
  • It should be noted that the HbA1c results, on their own, do not satisfy the definition of diabetes in the NHMS. Information about the definitions for measuring diabetes is available from the Diabetes biomarkers topic page of this chapter.
  • HbA1c test results do not confirm a specific diagnosis without consultation with a health professional.
  • Where HbA1c levels indicate a person is at risk of diabetes, prevention interventions might be considered such as lifestyle modifications to achieve HbA1c targets.2
  • The NHMS cut off reference ranges are based on measuring chronic glycemia periodically and this test may be repeated every 3 or 6 months depending on HbA1c levels and upon consultation with a health professional.
  • HbA1c levels are affected by conditions that affect red blood cell survival time or non-enzymatic glycation of haemoglobin.2
  • There are a number of different test methods for measuring HbA1c, which may produce different results. The data from this topic should therefore be used with caution when comparing HbA1c results from other studies using a different test method or equation.

Comparability with other surveys

The NHMS is the first ABS survey to collect biomedical data on diabetes.

Diabetes data has been collected in other non-ABS surveys. However, caution must be taken when interpreting results due to the differences in scope, assay and the instrument used, and any thresholds applied in the final analysis.


1 World Health Organization 2011, Use of Glycated Haemoglobin (HbA1c) in the Diagnosis of Diabetes Mellitus, <http://www.who.int/diabetes/publications/report-hba1c_2011.pdf>, Last accessed 16/07/2013.
2 Michael C d’Emden, Jonathan E Shaw, Peter G Colman, Stephen Colagiuri, Stephen M Twigg, Graham R D Jones, Ian Goodall, Hans G Schneider and N Wah Cheung 2012, The role of HbA1c in the diagnosis of diabetes mellitus in Australia, Medical Journal of Australia, <https://www.mja.com.au/journal/2012/197/4/role-hba1c-diagnosis-diabetes-mellitus-australia>, Last accessed 22/10/2013.
3 Jones GR, Barker G, Goodall I, Schneider HG, Shephard MD, Twigg SM 2011, Change of HbA1c reporting to the new SI units, Medical Journal of Australia, <https://www.mja.com.au/journal/2011/195/1/change-hba1c-reporting-new-si-units.pdf>, Last accessed 22/10/2013.
4 Diabetes Australia 2012, Diabetes Management in General Practice: Guidelines for Type 2 Diabetes, <http://www.diabetesaustralia.com.au/en/For-Health-Professionals/Diabetes-National-Guidelines/>, Last accessed 22/10/2013.

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