Alanine Aminotransferase (ALT)
Disclaimer: Information on this page is for educational purposes. Consult a physician to interpret your test results. Lissa Health helps track biomarker trends but does not replace medical advice.
What This Test Measures
ALT is an enzyme found mainly in hepatocyte cytoplasm. When liver cells are injured, ALT leaks into blood, making it one of the most sensitive markers of hepatocellular damage.
Elevation may be asymptomatic and found on routine screening. Levels correlate with injury extent but do not always reflect functional liver reserve.
ALT is interpreted with AST, bilirubin, and GGT to differentiate hepatitis, steatosis, and drug-induced liver injury.
Normal Ranges
| Group | Reference Range |
|---|---|
| Men | 0–41 U/L |
| Women | 0–31 U/L |
| Children | 0–31 U/L |
Reference ranges may vary by laboratory and assay method.
Causes of High Levels
- Acute and chronic hepatitis
- Fatty liver disease (NAFLD)
- Drug-induced liver injury
- Strenuous exercise
- Myopathy
Causes of Low Levels
- Significant decrease is uncommon
- End-stage cirrhosis
- Vitamin B6 deficiency (rare)
Test Preparation
- Fasting blood draw (8–12 hours)
- Avoid alcohol and heavy exercise for 24 hours
- Report all medications and supplements
Related Biomarkers
| Biomarker | Relationship |
|---|---|
| Aspartate Aminotransferase (AST) | AST/ALT ratio |
| Gamma-Glutamyl Transferase (GGT) | Cholestatic component |
| Total Bilirubin | Liver function |
FAQ
How often should I take this test?
Annually for screening; with liver disease — every 3–6 months.
What should I do if my result is abnormal?
Persistent elevation warrants hepatology consult, liver ultrasound, viral hepatitis panel.
Last updated: June 2026