ALT, the liver-specific enzyme ALT (SGPT)
An enzyme that leaks out of liver cells when they are irritated.
Also printed asAlanine Aminotransferase · ALT · SGPT · GPT · Alanine Transaminase
What it measures
An enzyme that leaks out of liver cells when they are stressed or inflamed.
The earliest routine signal of fatty liver, which sits at the centre of insulin resistance and future diabetes.
Why it matters for how long you stay well
A quietly raised level is the most common early sign of fat building up in the liver, and that same fat sits at the root of insulin resistance, blood-fat problems and heart risk decades later.
How it shows up in daily life
A liver holding extra fat rarely hurts. You may notice nothing at all, or only that you tire more easily after meals.
High and low readings
When it reads high
Liver cells under strain from fat, alcohol, medicines, or very hard exercise.
When it reads low
Low is fine.
What moves it
Daily life
- alcohol
- sugary drinks, sweets and refined carbohydrate
- weight around your middle
- walking and strength training, which lower it
- some herbal and bodybuilding supplements
Medicines known to shift it
- statins (can raise it)
- NSAIDs (can raise it)
- antibiotics (can raise it)
- GLP-1 medicines (lower it)
Listed so a result can be read in context. It is not advice to start, stop or change any medicine; that decision belongs with your physician.
Read it with
Markers that move this one, or that this one moves. One number read alone can mislead.
- Insulin resistance scoreObserved association
Insulin resistance score pushes it up
Insulin resistance parks fat inside your liver. A liver holding extra fat leaks more ALT into the blood, which is how a sugar problem shows up on a liver test.
- Triglycerides, blood fatsObserved association
As this rises, Triglycerides moves with it
A liver holding extra fat does two things at once. It leaks ALT, and it pushes extra triglycerides out into the blood, which is why the pair usually rises together.
- AST to ALT patternKnown mechanism
As this rises, AST to ALT pattern falls as it rises
ALT sits at the bottom of that fraction. A liver holding extra fat lifts ALT the most, which is what pushes the pattern below one.
- AST, a liver and muscle enzymeKnown mechanism
As this rises, AST moves with it
Both enzymes leak from the same irritated liver cells, so they usually rise together. What points at the cause is the ratio between them, not either number alone.
- GGT, the alcohol-sensitive enzymeObserved association
GGT moves with it
GGT and ALT both climb when the liver is holding extra fat, so they tend to move as a pair. A raised GGT on its own points somewhere else.
Common questions
What does ALT (SGPT) measure?
An enzyme that leaks out of liver cells when they are stressed or inflamed. The earliest routine signal of fatty liver, which sits at the centre of insulin resistance and future diabetes.
What does a high ALT result usually mean?
Liver cells under strain from fat, alcohol, medicines, or very hard exercise.
What does a low ALT result usually mean?
Low is fine.
What is the usual reference range for ALT?
A broad adult reference band is 7–45 U/L. For women the band is 7–35 U/L. Labs differ, so read your result against the band printed on your own report.
Educational only, not a diagnosis. A single number means little without your history and the rest of your panel, so discuss your own results with your physician.
Typical adult reference band
- Men
- 7–45 U/L
- Women
- 7–35 U/L
Labs differ. The band printed on your own report is the one that applies to your result.
Reported in U/L
Ageing relevance
3/5
A moderate ageing association; used in clinical longevity panels.
Worth knowing
This enzyme is far more specific to the liver than its partner AST, which also comes from muscle.
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