Liver function biomarkers

The liver is an essential organ and regulates most chemical levels in the body. It has many functions, including removing toxins from the blood, processing nutrients, and regulating hormones (Liver Foundation 2022a).

A range of factors, including fatty liver disease (where fat accumulates in the liver), infections (hepatitis), liver cancer and excessive alcohol consumption can prevent the liver from performing these functions well and if left untreated, can lead to liver damage. When the liver is inflamed or damaged, enzymes leak from the liver cells into the bloodstream. These enzymes are also found in other organs, such as the heart and muscles, so high levels may not always be due to a liver problem (Liver Foundation 2022b).

The indicators of liver function that were measured were:

• alanine aminotransferase (ALT)
• gamma glutamyl transferase (GGT).

The IHMHS provides an objective measurement of the number of people in Australia with elevated ALT and GGT levels. While these tests cannot diagnose the presence of liver disease, elevated levels for either test may indicate impaired liver function (Coates 2011; Liver Foundation 2022b).

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

This is the second time the ABS has collected information on ALT and GGT levels. Information on these biomedical indicators 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.

ALT and GGT 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.

ALT is an enzyme that is mainly found in your liver, but smaller amounts are found in your muscles, kidneys and other organs. Elevated levels of ALT are associated with liver damage and indicate a degree of liver inflammation (RCPA 2023).

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

ALT levels were measured at the Douglass Hanly Moir Pathology (DHM) laboratory by an Activated ALT assay. The ALT test measures the amount of ALT circulating in the blood at the time of the test, expressed as units per litre (U/L).

There is no consensus on the cut-off reference values for defining abnormal ALT levels for the Australian population, as there are currently several different methods that can be used to measure ALT. As such, cut-off reference values for normal and abnormal results were sourced from DHM laboratory reference ranges, taking the upper level of the normal range as the cut-off point.

The Royal College of Pathologists Australia (RCPA) uses a different reporting level for abnormal ALT. For adult females, the cut-off is >35 U/L. The cut-off for males is similar to above (>40 U/L) (RCPA 2024a).

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

• ALT results do not confirm a specific diagnosis without consultation with a health professional.
• There are several different test methods for measuring ALT which may produce different results. The data from this topic should therefore be used with caution when comparing ALT results from other studies using a different test method.
• Liver disease is associated with many health concerns and elevated ALT levels are not only associated with liver damage, but also with Type 2 diabetes mellitus, cardiovascular disease, stroke and metabolic syndrome (Coates 2011).

Gamma-glutamyl transferase (GGT) is a common enzyme found in many of the body’s tissues and organs, primarily in the liver. GGT is located on the plasma membranes of most cells and organ tissues, but more commonly in hepatocytes, and is routinely used in clinical practice to help indicate liver injury and as a marker of excessive alcohol consumption. GGT is considered one of the more sensitive indicators of liver function and elevated levels indicate poor liver function (Kunotsor 2016; Coates 2011; Liver Foundation 2022b).

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

GGT levels were measured at the DHM laboratory by the Szasz l-gamma-glutamly-3-carboxyl-4-nitroanilide method. The GGT test measures the amount of GGT circulating in the blood at the time of the test, expressed as units per litre (U/L).

There is no consensus on the cut-off reference values for defining abnormal GGT levels for the Australian population, as there are currently several different methods that can be used to measure GGT. Reference values for normal and abnormal results were sourced from DHM laboratory reference ranges, taking the upper level of the normal range as the cut-off point.

For adults, the RCPA has a reporting level for GGT for abnormal levels for females of >35 U/L and for males of >50 U/L; the normal ranges of 5–35 U/L for females and 5–50 U/L for males are known as harmonised reference intervals, intended for use by all pathology laboratories in Australia (RCPA 2024b).

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

• GGT results do not confirm a specific diagnosis without consultation with a health professional.
• There are several different test methods for measuring GGT, which may produce different results. The data from this topic should therefore be used with caution when comparing GGT results from other studies using a different test method.
• Liver disease is associated with many health concerns and elevated GGT levels are not only associated with liver damage, but also with Type 2 diabetes mellitus, cardiovascular disease, chronic alcohol abuse and pancreatic cancer (Coates 2011; Kunutsor 2016).

Coates P (2011), Liver function tests, Australian Journal for General Practitioners, 40(3):113-115, accessed 20/02/2025.

Kunutsor SK (2016), Gamma-glutamyltransferase – friend or foe within?, Liver International, 36(12):1723-1734, accessed 20/02/2025.

Liver Foundation (2022a), ‘About the liver’, Your Liver website (Liver Foundation), accessed 20/02/2025.

Liver Foundation (2022b), ‘Liver Tests Explained’, Your Liver website (Liver Foundation), accessed 20/02/2025.

Pathology Tests Explained (2023), Alanine Aminotransferase (ALT), Pathology Tests Explained website, accessed 20/02/2025.

Royal College of Pathologists of Australasia (RCPA) (2024a), ’Alanine Aminotransferase‘, RCPA Manual, RCPA website, accessed 20/02/2025.

Royal College of Pathologists of Australasia (RCPA) (2024b), ‘Gamma Glutamyltransferase’, RCPA Manual, RCPA website, accessed 20/02/2025.