Typical reference ranges
| ALT level | How it is usually described | Common causes |
|---|---|---|
| Up to the lab's limit (often 40 U/L) | Normal | — |
| 1–5 × upper limit | Mildly raised | Fatty liver, alcohol, medicines, chronic hepatitis B or C |
| 5–15 × upper limit | Moderately raised | Acute or chronic hepatitis, medicine injury |
| Above 15 × upper limit | Markedly raised | Acute viral hepatitis, paracetamol overdose, low blood flow to the liver |
Ranges based on: MedlinePlus; ACG Clinical Guideline. Full references are listed at the end of this page.
Use your own lab's range. Reference ranges differ between labs, analysers and methods, and with age, sex and pregnancy. The range printed on your report takes priority over the figures here.
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Common causes of a raised ALT
- Fatty liver (MASLD): the commonest cause worldwide, linked with weight gain, diabetes and high triglycerides.
- Viral hepatitis: hepatitis B and C (often silent for years), and hepatitis A and E, which spread through contaminated food and water.
- Alcohol: usually with AST higher than ALT.
- Medicines and supplements: statins (usually mild), anti-TB drugs, some antibiotics, anti-epileptics, paracetamol in excess, and herbal products.
- Less common: autoimmune hepatitis, haemochromatosis, Wilson disease, coeliac disease and thyroid problems.
What usually happens next
For a mildly raised ALT, doctors often repeat the test, review medicines and alcohol, and check hepatitis B surface antigen, hepatitis C antibody, a lipid profile, sugar and an ultrasound for fatty liver. A higher or rising ALT is investigated sooner.
ALT and AST together
When AST is more than twice ALT, alcohol-related liver disease is more likely. In fatty liver and viral hepatitis, ALT is usually higher than AST.
Frequently asked questions
What is a normal SGPT level?
Most labs use up to about 40 U/L; healthy upper limits are about 33 U/L for men and 25 U/L for women.
Can fatty liver raise ALT?
Yes. It is the most common cause of a mildly raised ALT.
Can ALT go back to normal?
Often yes, once the cause is treated, for example weight loss in fatty liver or stopping a medicine.
Does a normal ALT rule out liver disease?
No. Advanced scarring (cirrhosis) can have a normal ALT.