What AST Actually Measures
AST — short for aspartate aminotransferase (older reports may call it SGOT) — is an enzyme that helps your cells turn amino acids into energy. It sits inside cells, so normally only a small amount circulates in your blood. The highest concentrations are in your liver, but AST is also found in your heart, skeletal muscle, kidneys, brain and red blood cells. When any of those cells are injured, AST leaks into the bloodstream — which is why a raised AST is a flag that tissue somewhere, most often the liver, is under stress.
Because AST is not unique to the liver, it is almost never interpreted on its own. It is read alongside ALT (alanine aminotransferase), an enzyme far more specific to the liver. Together, AST and ALT are the two "transaminases" at the heart of the liver function test (LFT) panel your GP orders.
How AST Is Reported in Australia
Australian pathology labs report AST in units per litre (U/L). There is no single national reference interval — each lab calibrates its own analysers and publishes its own range — so the figure in the "reference interval" column next to your result is the one that counts. As a general guide, most Australian adults sit in the ranges below.
Normal AST Range
| Group | Typical AST reference range (U/L) |
|---|---|
| Adult women | ~5–35 |
| Adult men | ~5–40 |
| Commonly reported upper limit | ~40 U/L (some labs up to 45) |
Men tend to have a slightly higher upper limit than women because they carry more muscle mass. A single result a few points above the top of the range is extremely common and rarely a problem on its own — even a hard gym session or a long run the day before can nudge AST up. What your GP looks at is the size of the rise, whether it persists on a repeat test, and how it sits relative to ALT.
What a High AST Means
A raised AST has two broad sources — liver and non-liver — and telling them apart is the whole point of looking at the rest of your panel.
Liver causes (usually raise ALT as well):
- Fatty liver disease (MASLD/NAFLD) — the most common cause of a mildly raised AST in Australia, linked to weight, type 2 diabetes and metabolic health.
- Alcohol-related liver injury — classically raises AST more than ALT.
- Viral hepatitis (B or C).
- Medications and supplements — including some statins, paracetamol in overdose, and certain herbal products.
- Cirrhosis or other chronic liver disease.
Non-liver causes (often raise AST without raising ALT much):
- Strenuous exercise or muscle injury — AST is abundant in skeletal muscle.
- A recent intramuscular injection.
- Heart muscle damage (for example after a heart attack).
- Haemolysis — red cells breaking down, sometimes simply from how the sample was collected.
The height of the result is a clue too. A mild rise (under about three times the upper limit) is usually fatty liver, alcohol or medication. A marked rise (ten or more times the upper limit) points to acute liver-cell injury — viral hepatitis, a drug or toxin such as a paracetamol overdose, or reduced blood flow to the liver — and needs prompt medical assessment.
AST vs ALT — Reading Them Together (the AST/ALT ratio)
Because ALT is more liver-specific, comparing the two enzymes is one of the most useful things your GP does with these numbers. The AST/ALT ratio (sometimes called the De Ritis ratio) gives a quick steer:
- Ratio under 1 (ALT higher than AST): typical of fatty liver disease and chronic viral hepatitis.
- Ratio around 2 or above, with a raised GGT: suggests alcohol-related liver disease.
- Ratio rising above 1 in someone with known liver disease: can indicate progression toward cirrhosis.
This is exactly why AST is rarely actioned alone. For the full panel — ALT, GGT, ALP, bilirubin and albumin — see our guide to reading Australian liver function tests.
What a Low AST Means
A low AST is almost never a cause for concern and usually needs no action. Very low levels are occasionally linked to vitamin B6 (pyridoxine) deficiency, which the enzyme depends on to work. If your AST is below the reference range and you feel well, it is not something to worry about.
When You Need an AST Test
Your GP will typically include AST (as part of an LFT) when:
- You have symptoms that could point to the liver — fatigue, nausea, upper-right abdominal discomfort, or yellowing of the skin or eyes (jaundice).
- You are being monitored — for example on a statin or other medication that can affect the liver, or with known fatty liver, hepatitis or higher alcohol use.
- It is part of a routine health check or a general blood screen.
Will Medicare Cover an AST Test?
Yes. AST is not ordered as a stand-alone item — it comes bundled in the liver function test (LFT) group, which Medicare bulk-bills when your GP provides a referral and there is a clinical reason for the test. Most Australian pathology providers bulk-bill LFTs, so you usually pay nothing out of pocket. If you request testing without a GP referral (through a private or "self-request" service), you may be charged a fee.
How to Track Your AST Over Time
For AST, the trend matters more than any single reading. A one-off result just over the line means far less than a number climbing across several tests — or one steadily falling as fatty liver improves with weight loss. Keeping your AST, ALT and GGT side-by-side over time is the clearest way to see whether your liver health is moving in the right direction, and it gives your GP useful context at your next appointment. You can store and chart every result in one place with BloodTrack.
This guide is general information for an Australian audience and is not a substitute for personal medical advice. Reference ranges vary between laboratories — always read your result against your own lab's printed range, and discuss any abnormal or persistent result with your GP.