ALT Liver Enzyme: Normal Levels by Age
Updated June 2026
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Last updated: June 2026 - Reviewed by the Apexzen editorial team
Part of: Blood Biomarkers Guide
What is ALT? Alanine aminotransferase is an enzyme that lives mostly inside liver cells. When those cells are injured or inflamed, ALT leaks into the bloodstream, so a higher ALT on a blood test is a common early signal of liver stress. It is usually measured as part of a liver panel and interpreted alongside other enzymes such as AST. People often ask about normal ALT by age, but in practice the reference range depends more on the lab and your sex than on age alone.
Optimal and reference range
The figures below are typical lab reference ranges, which vary by lab and individual. Your own report's range is the one that counts. Discuss your results with your doctor or clinician.
| Group | Typical reference range | Units |
|---|---|---|
| Adult men | about 7 to 55 | U/L |
| Adult women | about 7 to 45 | U/L |
Ranges vary by lab and individual; discuss your results with your doctor.
What affects ALT and what helps
Many causes of a raised ALT respond to lifestyle changes made under a clinician's guidance:
- Reach and maintain a weight your doctor recommends, since fatty liver is a leading cause of mildly high ALT.
- Limit or avoid alcohol, which directly stresses the liver.
- Favor a balanced diet and limit sugary drinks and ultra-processed foods.
- Review any medications and supplements with your doctor, as some can raise liver enzymes.
Strenuous exercise just before a blood draw can also nudge ALT upward, which is one reason your doctor may repeat the test before acting.
When to talk to your doctor
See your doctor if your ALT is above your lab's range, especially if it stays high on a repeat test, or if you have symptoms such as yellowing of the skin or eyes, dark urine, or persistent fatigue. Your clinician can look at the full liver panel, your history, and any medications, and decide whether further testing is needed.
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Take the QuizFrequently asked questions
Do normal ALT levels change with age?
The reference range depends more on the lab and your sex than on age. Your own report's range is the one to use, and your doctor will interpret your result against it.
Is a slightly high ALT dangerous?
A mild rise is common and often reversible, but it should be checked. Your doctor decides whether to repeat the test or investigate further.
Can a supplement lower ALT?
No supplement reliably lowers ALT, and some can raise liver enzymes. Focus on the lifestyle steps above and talk to your doctor before adding anything.
Related reading: eGFR: What Your Kidney Function Number Means and Blood Biomarkers Guide.
Sources: National Institutes of Health (NIH); Mayo Clinic - liver enzyme and ALT guidance.
This article is for educational purposes only and is not medical advice. These statements have not been evaluated by the Food and Drug Administration. Apexzen products are not intended to diagnose, treat, cure, or prevent any disease. Always consult a qualified healthcare provider before changing your diet, supplements, or treatment.