ALT (Alanine Aminotransferase): Normal Range, High & Low Causes
What ALT measures
ALT is an enzyme found mostly in the liver. When liver cells are injured, ALT leaks into the blood, so a raised level is a sensitive sign of liver irritation.
ALT reference ranges
| Category | Conventional units | SI units |
|---|---|---|
| Typical adult range | 7 – 55 U/L | Same unit (U/L, IU/L) |
Some labs set lower upper limits, particularly for women. U/L and IU/L are the same number.
Common causes of a high result
- Fatty liver disease (metabolic-associated steatotic liver disease)
- Alcohol
- Viral hepatitis B or C
- Medicines and supplements, including high-dose paracetamol (acetaminophen) and some statins or antibiotics
- Intense exercise before the test
- Autoimmune or inherited liver conditions
Common causes of a low result
- A low ALT is usually not a concern
How to prepare for the test
Avoid alcohol and heavy exercise for a day or two before the test, and tell your clinician about every medicine and supplement you take.
How often to retest
A mildly raised ALT is often repeated in a few weeks. Your clinician sets follow-up.
Track ALT over time
Upload your reports and Labgist plots every ALT result on one timeline, converts units and shows what changed.
Get the appFrequently asked questions
What is a normal ALT level?
Roughly 7–55 U/L for adults, with variation between labs.
What is the difference between ALT and AST?
Both are liver enzymes. ALT is more specific to the liver, while AST is also found in muscle and the heart. The pattern between them can hint at the cause.
Can ALT be raised by exercise or supplements?
Yes. Hard workouts, some herbal and bodybuilding supplements and many medicines can raise ALT temporarily.
Related tests
Sources
This page is general education and was last updated 2026-10-30. It is not a substitute for medical advice. See our editorial approach.