What Does ALT (Alanine Aminotransferase) Mean?
ALT is a liver enzyme that leaks into the blood when liver cells are stressed or damaged. Mild elevations are common and often relate to fatty liver, alcohol, or medications.
What ALT (Alanine Aminotransferase) Measures
ALT is an enzyme found mostly inside liver cells. Damaged or stressed liver cells release ALT into the bloodstream, so elevated ALT is one of the most sensitive markers of liver injury. Mild elevations are common and don't always indicate serious disease.
Normal Ranges
Normal (men)7–55 U/L
Normal (women)7–45 U/L
Mildly elevated1–3× upper limit
Significantly elevated> 3× upper limit
Reference ranges may vary slightly by lab. Always use the range provided on your specific test report.
What Affects Your ALT (Alanine Aminotransferase) Level
- Non-alcoholic fatty liver disease (most common cause of mild elevation)
- Alcohol intake
- Certain medications (acetaminophen, statins, antibiotics)
- Viral hepatitis (A, B, C)
- Obesity and metabolic syndrome
- Intense exercise (transient rise)