Biomarker · Liver
Alanine aminotransferase (ALT)
ALT is a liver enzyme that rises when liver cells are stressed or damaged. Learn what an ALT test measures and what can raise it.
Written by LON6EVITY Editorial Team · Last updated
Overview
ALT is an enzyme found mostly in the liver. When liver cells are injured, ALT leaks into the bloodstream.
Why it matters
ALT is one of the main markers used to check liver health, often as part of a liver function test or comprehensive metabolic panel.
Higher results
Raised ALT can be linked to fatty liver, alcohol, viral hepatitis, some medications and supplements, and other liver conditions. Mild, temporary rises can follow intense exercise. The pattern with other liver tests helps clinicians interpret it.
How the test is performed
A standard blood sample.
Reference ranges
Reference ranges and targets differ between laboratories, units and guidelines, and depend on age, sex, method and your overall clinical picture. A single result is not a diagnosis — interpret it with a qualified clinician.
Factors that can affect the result
- Alcohol
- Excess weight and fatty liver
- Medications and supplements
- Intense exercise
- Viral infections
Questions people commonly ask
- Does a high ALT mean liver disease?
- Not necessarily. Mild rises are common and can be temporary; your clinician may repeat the test or order further checks.
Related biomarkers
Related tests
Related topics
Understand your biomarkers in context
What does this mean for your own health data? Log your results, follow trends over time and bring an organised summary to your next doctor's appointment.
Sources
- ALT Blood Test. MedlinePlus, U.S. National Library of Medicine.
- Liver Function Tests. MedlinePlus, U.S. National Library of Medicine.