What ALT Actually Measures
ALT — short for alanine aminotransferase (older reports may call it SGPT) — is an enzyme that helps your cells process amino acids for energy. Unlike most enzymes on your panel, ALT is found almost entirely in the liver. That makes it the most liver-specific number in a standard blood test: when ALT is raised, the liver is nearly always the source, so it is the headline marker doctors watch for liver-cell injury.
ALT is read together with AST (aspartate aminotransferase) — the two "transaminases" — as part of the liver function test (LFT) panel your GP orders.
How ALT Is Reported in Australia
Australian pathology labs report ALT in units per litre (U/L). There is no single national reference interval — each lab publishes its own — 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 ALT Range
| Group | Typical ALT 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. A single result a little above the top of the range is very common and rarely a problem on its own — what your GP looks at is the size of the rise, whether it persists on a repeat test, and how it compares to AST.
What a High ALT Means
Because ALT is so liver-specific, a raised ALT almost always reflects liver-cell stress. The most common causes in Australia are:
- Fatty liver disease (MASLD/NAFLD) — by far the most common reason for a mildly raised ALT, linked to weight, type 2 diabetes and metabolic health.
- Alcohol-related liver injury.
- Viral hepatitis (B or C) — which can cause very high ALT.
- Medications and supplements — including some statins, paracetamol in overdose, and certain herbal products.
- Cirrhosis or other chronic liver disease.
The height of the rise helps 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) suggests 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.
ALT vs AST — Reading Them Together (the AST/ALT ratio)
ALT and AST tell a fuller story together than either does alone. Because AST is also found in muscle and heart, comparing the two — the AST/ALT ratio (De Ritis ratio) — helps point to the cause:
- 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.
For the rest of the panel — AST, GGT, ALP, bilirubin and albumin — see our guide to reading Australian liver function tests.
What a Low ALT Means
A low ALT is almost never a concern and needs no action. It is occasionally linked to vitamin B6 (pyridoxine) deficiency, which the enzyme relies on. If your ALT is below the range and you feel well, there is nothing to worry about.
When You Need an ALT Test
- 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 — 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 general blood screen.
Will Medicare Cover an ALT Test?
Yes. ALT is not ordered on its own — 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. Most Australian pathology providers bulk-bill LFTs, so you usually pay nothing. Tests requested without a GP referral may attract a fee.
How to Track Your ALT Over Time
For ALT, 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 ALT, AST and GGT side-by-side over time is the clearest way to see whether your liver health is heading the right way. You can store and chart every result 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.