Gamma-GT (GGT)
GGT is a liver enzyme that is especially sensitive to alcohol and to problems with the bile ducts — the tubes that carry bile out of the liver. A result inside the range on your report is reassuring. A raised GGT on its own is not a diagnosis, but it is worth talking through with your GP alongside your other liver markers. Most causes are manageable once the reason is clear.
Standard CareWhat is gamma-gt (ggt)?
Gamma-glutamyl transferase (GGT) is an enzyme — a protein that speeds up chemical reactions — found mainly in the liver. It is especially helpful when bile duct disorders are being investigated: the bile ducts are the small tubes that carry bile (the digestive fluid your liver produces) from the liver to the small intestine. When the liver is injured or the flow of bile is blocked, the GGT level rises in the blood. GGT is usually ordered as part of Liver Function Tests (LFTs) — a panel of tests that assesses the health of your liver. The panel also includes ALT (alanine aminotransferase), AST (aspartate aminotransferase), ALP (alkaline phosphatase), albumin, and bilirubin. One of GGT's most practical uses is helping interpret a raised ALP: because ALP comes from both the liver and bones, a raised GGT alongside a raised ALP points the GP towards the liver or bile ducts as the source rather than bone.
Why is it tested?
Your GP may include GGT in a liver panel for several reasons. Most often it is to screen for liver and bile duct conditions, or to look into symptoms such as jaundice (a yellowing of the skin or the whites of the eyes), abdominal pain, fatigue, or nausea. Because GGT is so sensitive to alcohol, it also helps assess alcohol-related liver stress. It is useful for interpreting a raised ALP result too, and for keeping track of a known liver or bile duct condition over time.
Reference range (Australia)
Men tend to sit higher than women. The AACB/RCPA Australasian Harmonised Reference Intervals (Table 1) specify 5–50 U/L for males and 5–35 U/L for females. The range printed on your own report is the authoritative figure for your result.
Reference intervals vary between laboratories. Always use the range printed on your own report.
What your result means
A low GGT result is not clinically significant. Your GP will focus on the overall LFT panel and your clinical picture.
An in-range GGT result is generally reassuring — it suggests your liver and bile ducts are not under significant stress. Your GP reads it alongside the rest of the LFT panel to build the complete picture.
A raised GGT suggests the liver is under stress, the bile ducts are affected, or that the liver has been processing alcohol (GGT is unusually sensitive to it, even at modest amounts). Several liver conditions can lift it — alcoholic liver disease, viral hepatitis (liver inflammation caused by hepatitis viruses), and metabolic-dysfunction fatty liver disease (MAFLD, previously called NAFLD, where fat builds up in liver cells). Bile duct problems such as gallstones or tumours can raise it as well, and so can inflammation, infections, and certain autoimmune diseases (where the immune system mistakenly targets the liver or bile ducts). A raised GGT alongside a raised ALP is a useful clue that the source of the ALP elevation is more likely the liver or bile ducts than bone. Your GP will look at the full LFT panel, your alcohol intake, medications, and any symptoms before drawing conclusions. A mildly raised GGT, particularly without other abnormal liver markers, often has a manageable and straightforward explanation.
What can affect your result
GGT is particularly sensitive to alcohol — even moderate or short-term increases in alcohol intake can raise GGT, and it often returns towards normal within a few weeks of reducing or stopping drinking. This sensitivity makes GGT one of the more useful markers when alcohol-related liver stress is being considered. Beyond alcohol, a few other things raise GGT. Viral hepatitis is one, and so is metabolic-dysfunction fatty liver disease (MAFLD), which is linked to obesity, type 2 diabetes, and metabolic syndrome (a cluster including high blood pressure, raised blood sugar, and abnormal cholesterol). Anything that blocks or inflames the bile ducts — gallstones, for instance — will lift it too. Some medications can, including anticonvulsants (medicines used for epilepsy). Less commonly, liver tumours or autoimmune liver conditions are the cause.
When to act
If your GGT is raised, it is worth discussing at your next GP appointment rather than something to act on alone. They will consider whether other markers on your LFT panel are also raised, and will ask about alcohol intake, medications, and any symptoms. If your ALP is also elevated, the combination is a useful pointer towards a liver or bile duct source rather than bone. Depending on the pattern, your GP may recommend a repeat test after a period of reduced alcohol intake, a medication review, an ultrasound of the liver and bile ducts, or referral to a liver specialist (hepatologist) for further assessment. This page is general information and is not a substitute for advice from your GP.
Frequently asked questions
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