Liver
ALT
LOINC 1742-6 · U/L
Ranges
Reference range: 7–56 U/L
What it is
ALT (alanine aminotransferase) is an enzyme found mostly in the liver. It leaks into the blood when liver cells are injured.
Why it matters
ALT is one of the most specific blood markers of liver-cell injury, central to checking liver health.
What high values can mean
A higher value suggests liver-cell stress or injury, commonly from fatty liver, alcohol, medications or viral hepatitis.
What low values can mean
A lower value is generally not a concern.
How to improve it
Weight management, limiting alcohol, an active lifestyle and a balanced diet are key for the common causes of raised ALT.
Food & lifestyle
Reducing sugary drinks, refined carbs and alcohol and favouring vegetables and whole foods helps fatty liver, a top cause.
Preparing for the test
Often part of a liver panel; fasting is not specifically required — follow your lab.
When to talk to a doctor
Discuss a persistently raised ALT with a doctor, who will look at AST and your overall picture.
Related markers
Sources
- MedlinePlus (NIH)
- Testing.com (AACC)
Content reviewed on June 26, 2026
Medical disclaimer
This content is for educational purposes only. It is not medical advice and does not diagnose, treat, or prevent any condition. Reference ranges vary between laboratories — always use the range printed on your report and discuss your results with a healthcare professional.
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