Iron

Iron is an essential dietary mineral, with important functions including the production of haemoglobin, DNA synthesis and muscle metabolism. Almost two thirds of the body’s iron is found in haemoglobin, which transports oxygen to tissues around the body. The body cannot produce its own iron, so the body’s iron levels are reliant on dietary intake (NHMRC 2013; WHO 2020a, b; Gibson and Friel 2024).  

The main dietary sources of iron are meat, eggs, legumes, dark leafy greens, nuts and seeds. The 2013 National Health and Medical Research Council (NHMRC) Nutrient Reference Values for Australia and New Zealand for iron includes Adequate Intakes for infants, Estimated Average Requirements and Recommended Dietary Intakes for older infants, young children, and adults as individuals (NHMRC 2013).

Iron deficiency can lead to fatigue, tiredness, and decreased immunity. Iron deficiency is also the leading cause of anaemia, which is the most prevalent nutritional deficiency worldwide impacting an estimated 33% of the world’s population (WHO 2011; Gibson and Friel 2024).

Biomarkers that were collected to measure iron in the body were:

• haemoglobin (Hb)
• serum ferritin
• soluble transferrin receptor (sTfR).

To assist in interpreting ferritin levels, C-reactive protein (CRP) levels were also measured (to detect presence of inflammation). 

Laboratory test information, including analysis methods and machines used to measure iron biomarkers, is available from the Downloads page.

This is the second time the ABS has collected information on iron biomarkers (serum ferritin, CRP, sTfR and Hb). Information on these four biomarkers was previously collected in the NHMS 2011–12 and the NATSIHMS 2012–13. For information on time series comparability, see Comparing biomedical collections over time.

Iron biomarkers have been collected in other non-ABS surveys. However, caution must be taken when interpreting results for serum ferritin, CRP, sTfR and Hb due to the differences in scope, assay and the instrument used for each test, and any thresholds applied in the final analysis.

Ferritin is a blood protein that stores iron. In the body, small amounts of ferritin circulate in the blood and in most healthy persons the concentration of ferritin in blood is an effective measure of the body’s total iron stores. While normal ferritin concentrations vary by age and sex, a low ferritin concentration indicates iron deficiency. A low ferritin value is the first stage indicator of IDA. A high ferritin level suggests risk of iron overload, noting the cut-offs for risk of iron overload are different for ‘apparently healthy’ and ‘non-healthy’ individuals (WHO 2020a, b; Gibson and Friel 2024).

Ferritin concentrations are raised in inflammation (with or without infection), therefore, people with inflammation (defined in the IHMHS as a CRP level of >10 mg/L) are excluded from the published ferritin results. All serum ferritin results without this exclusion are available in the DataLab microdata products.

Serum ferritin results were obtained for persons aged 12 years and over who provided a blood sample. Fasting was not required for this test.

Serum ferritin levels were measured at the Douglass Hanly Moir Pathology (DHM) laboratory, by an Ultrasensitive immunoturbidimetric assay. The ferritin test measures the amount of ferritin circulating in the blood at the time of the test, expressed as µg/L.

Levels of ferritin can be affected by certain health conditions, infection or inflammation. In 2020, the World Health Organization (WHO) released new guidelines for reporting serum ferritin levels that include ranges for ‘apparently healthy’ and ‘non-healthy’ individuals, summarised in the table below. WHO also recommends excluding individuals with elevated inflammatory markers, such as CRP, when analysing serum ferritin results because levels tend to increase when inflammation is present (WHO 2020a, b).

People with a CRP level >10 mg/L were excluded from serum ferritin analysis in line with WHO’s recommendation.

Points to be considered when interpreting data for this topic include the following:

• Low ferritin results do not confirm a specific diagnosis of deficiency without consultation with a health professional.
• Levels of ferritin can be affected by infection or inflammation. Therefore, people with inflammation, defined as a CRP of >10 mg/L, were excluded from the published ferritin results.
• There are several different test methods to measure ferritin levels and each test method may produce different results. The data from this topic should therefore be used with caution when comparing ferritin results from other studies that use a different test method.

CRP is an acute phase protein made by the liver. Acute phase proteins are a class of proteins in blood that change concentration in response to inflammation. As a result, CRP is a non-specific marker of inflammation and infection (WHO 2014a).

CRP is not used for screening in a clinical setting, but the measurement of CRP assists with interpreting the serum ferritin results that can be affected by inflammation (Gibson and Friel 2024).

CRP results were obtained for persons aged 12 years and over who provided a blood sample. Fasting was not required for this test.

CRP levels were measured at the DHM laboratory, by a Turbidimetric/Immunoturbidimetric assay. The CRP test measures the amount of CRP circulating in the blood at the time of the test, expressed as mg/L.

There is no consensus on the epidemiological cut-off reference values for measuring CRP. The test reference range for normal CRP levels is <5 mg/L, however research shows that CRP levels >10 mg/L are indicative of an acute infection or inflammation (WHO 2014a). The IHMHS defines CRP levels >10 mg/L as elevated CRP. People with elevated CRP are excluded from serum ferritin analysis.

CRP data is collected to assist in the interpretation of ferritin results and is not currently included in ABS publications. However, CRP results are available in DataLab microdata products.

Points to be considered when interpreting data for this topic include the following:

• CRP test results cannot be used for a specific diagnosis of deficiency, but in consultation with a health professional may be used to interpret serum ferritin results.
• There are several different test methods to measure CRP levels and each test method may produce different results. The data from this topic should therefore be used with caution when comparing CRP results from other studies using a different test method.

sTfR is an iron related protein that is important in the process of carrying iron to body cells. It can be used as a measure of iron levels and is not as affected by infection or inflammation to the extent of other measures, such as serum ferritin. sTfR levels are elevated if there is an increased demand for iron, that is, levels increase in IDA or when iron stores are low. When serum ferritin results indicate depleted iron stores, sTfR can be used to assess the severity of the iron depletion (WHO 2014b, Gibson and Friel 2024).

sTfR results were obtained for persons aged 12 years and over who provided a blood sample. Fasting was not required for this test.

sTfR levels were measured at the DHM laboratory, by a particle enhanced immunoturbidimetric assay. The sTfR test measures the amount of sTfRs circulating in the blood at the time of the test, expressed as mg/L.

There is no consensus on the epidemiological cut-off reference values for measuring sTfR in the blood. The cut-off values for reporting sTfR levels are based on laboratory ranges and should be considered along with serum ferritin results when assessing population iron status. This is done by assessing the proportion of the population below serum ferritin thresholds for iron deficiency along with the proportion of the population above sTfR cut-offs values (WHO 2014b).

Points to be considered when interpreting data for this topic include the following:

• sTfR test results do not confirm a specific diagnosis of deficiency without consultation with a health professional.
• There are several different test methods to measure sTfR levels and each test method may produce different results. The data from this topic should therefore be used with caution when comparing sTfR results from other studies using a different test method.

Hb is a protein found in red blood cells that helps transport oxygen from the lungs to the rest of the body. Iron is an essential part of the Hb molecule, this means that Hb concentration can be used to test for IDA (Pathology Tests Explained 2023).

Anaemia is caused by a decrease in either the number of red blood cells in the body or the quantity of haemoglobin within red blood cells. A reduction in either, means that the heart must work harder to ensure that muscles and organs get the oxygen they need (Gibson and Friel 2024).

Hb results were obtained for persons aged 12 years and over who provided a blood sample. Fasting was not required for this test.

Hb levels were measured at the DHM laboratory, by a Spectrophotometric method after stabilisation with sodium laurel sulphate. The Hb test measures the amount of Hb circulating in the blood at the time of the test, expressed as g/L.

Abnormally low levels of Hb indicating a risk of IDA are defined differently for males and females, young people, and pregnant women. Cut-off reference values for normal and abnormally low (at risk of IDA) results were sourced from the WHO guidelines and presented in the table below (WHO 2011). These guidelines are based on epidemiological data and publications of major clinical trials.

Points to be considered when interpreting data for this topic include the following:

• Hb results do not confirm a specific diagnosis of deficiency without consultation with a health professional.
• Residential elevation above sea level and smoking are known to increase haemoglobin concentrations. Consequently, the prevalence of Hb deficiency may be underestimated in persons residing at high altitudes and among smokers when standard Hb cut-offs are applied (Gibson and Friel 2022).
• There are several different test methods for measuring Hb, which may produce different results. The data from this topic should therefore be used with caution when comparing Hb results from other studies using a different test method or equation.

Gibson RS, Friel JK (2024), ‘Iron’, Principles of Nutritional Assessment: 3rd Edition, Nutritional Assessment website, accessed 20/02/2025.

National Health and Medical Research Council (NHMRC) (2013), ‘Iron’ Nutrient Reference Values for Australia and New Zealand, Eat for Health website, accessed 20/02/2025.

Pathology Tests Explained (2023), Haemoglobin, Pathology Tests Explained website, accessed 20/02/2025.

World Health Organization (WHO) (2011), Haemoglobin concentrations for the diagnosis of anaemia and assessment of severity, WHO, accessed 20/02/2025.

World Health Organization (WHO) (2014a), C-reactive protein concentrations as a marker of inflammation or infection for interpreting biomarkers of micronutrient status, WHO, accessed 20/02/2025.

World Health Organization (WHO) (2014b), Serum transferrin receptor levels for the assessment of iron status and iron deficiency in populations, WHO, accessed 20/02/2025.

World Health Organization (WHO) (2020a), WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations, WHO, accessed 20/02/2025.

World Health Organization (WHO) (2020b), Serum ferritin concentrations for the assessment of iron status in individuals and populations: technical brief, WHO, accessed 20/02/2025.