Aspartate Transaminase (AST)
AST is an enzyme your liver releases into the blood when its cells are stressed or damaged. Because smaller amounts also live in your heart and muscle, a raised result is not always about the liver. A result inside the range on your report is reassuring. A raised result is worth a chat with your GP, who reads it alongside your other liver markers. Many mild rises settle once the cause, often a medication, alcohol or muscle strain, is found.
Standard CareWhat is aspartate transaminase (ast)?
Aspartate aminotransferase (AST) is an enzyme — a protein that speeds up chemical reactions — found in many tissues in the body. Unlike its close relative ALT (alanine aminotransferase), which lives mainly in the liver, AST is found mostly in the liver but also in red blood cells, heart and other muscles. This broader distribution matters: a raised AST is not always a liver signal. When the liver or other cells that contain AST are damaged, they release AST into the bloodstream where it can be picked up in a blood test. AST is usually measured as part of the Liver Function Tests (LFTs) — a standard panel that includes ALT, GGT (gamma-glutamyl transferase), ALP (alkaline phosphatase), albumin, and bilirubin. Reading AST alongside its panel companions is what lets your GP distinguish liver injury from other causes such as heart or muscle damage.
Why is it tested?
Your GP may order AST — almost always as part of a full LFT panel — for several reasons. Most often it is to check general liver health during a routine screen, or to look into symptoms such as jaundice (a yellowing of the skin or eyes), lasting fatigue, nausea, or discomfort on the right side of the abdomen. It is also used to see whether a medication or supplement is affecting your liver, and to keep an eye on a known liver condition such as viral hepatitis (liver inflammation caused by hepatitis A, B, or C viruses) or fatty liver disease (where fat builds up in liver cells). Paired with ALT, it also helps your GP read the AST:ALT ratio. Because AST lives in the heart and muscles as well as the liver, it can also rise with a heart attack or muscle injury — context your GP will consider when interpreting your result.
Reference range (Australia)
Men tend to sit slightly higher than women. The AACB/RCPA Australasian Harmonised Reference Intervals specify 5–35 U/L for males and 5–30 U/L for females. The range 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 AST result is rarely a concern and does not usually signal a health problem. Your GP will read it in the context of the full LFT panel and your overall clinical picture.
An in-range AST result is generally reassuring — it suggests liver cells and other AST-containing tissues are not under significant stress. Your GP reads it alongside the rest of the LFT panel to build a complete picture of liver health.
A raised AST means cells containing this enzyme have been releasing it into your blood — a sign of tissue stress or damage. The most common liver-related causes include alcohol-related liver stress, viral hepatitis, fatty liver disease, and medication effects. AST levels also rise due to non-liver conditions including heart attack and muscle injury, which is why your GP reads AST alongside ALT and the rest of the panel rather than in isolation. The AST:ALT ratio gives useful additional information. Usually ALT is higher than AST; if alcohol is the main contributor to cirrhosis, this ratio can reverse, with AST more than twice the level of ALT. A ratio greater than 1 can also be suggestive of advanced fibrosis (scarring) or cirrhosis (extensive liver scarring). A mildly raised AST, particularly without symptoms, is often temporary and manageable — your GP will decide whether monitoring, a repeat test, or further investigation is the right next step.
What can affect your result
AST rises when liver, heart, or muscle cells are damaged or stressed, so a few different things can move it. Alcohol is a common driver, since alcohol-related liver disease lifts AST. Many medications can raise liver enzymes for a time too — statins (cholesterol-lowering medicines), paracetamol at higher or prolonged doses, some antidepressants, amiodarone (a heart-rhythm medicine), and certain herbal supplements. Viral infections such as hepatitis A, B, and C injure liver cells directly. Excess body weight and fatty liver disease are among the most common causes of a steadily raised AST in Australia. Because AST also lives in muscle, intense exercise can nudge it up briefly (usually mild, and it settles quickly). A heart attack or a significant muscle injury can raise it sharply — which is exactly why the AST:ALT pattern matters. The AST:ALT ratio — comparing the levels of these two related liver enzymes — can help your GP narrow down the pattern. Usually ALT is higher than AST; if alcohol is the primary driver of cirrhosis, the ratio can reverse, with AST being more than twice the level of ALT.
When to act
If your AST is raised, that is worth raising with your GP rather than something to act on alone. They will look at how far the result sits above the reference interval on your report, how it compares with your ALT and the rest of the LFT panel, and what the AST:ALT ratio suggests. They will also ask about your medications, alcohol intake, exercise habits, and any symptoms. Depending on the pattern, your GP may recommend watching and waiting with a repeat test, reviewing a medication, organising an ultrasound, or referring you to a liver specialist (hepatologist or gastroenterologist) for further assessment. If you also have jaundice (yellowing of the skin or eyes), persistent fatigue, nausea, dark urine, or right-sided abdominal pain, let your GP know promptly — these symptoms together provide important additional context. This page is general information and is not a substitute for advice from your GP.
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