Liver Enzyme ALT

Alanine aminotransferase (ALT) is a liver enzyme measured in a blood sample to check for liver cell injury, and most healthy adults sit around 7 to 55 U/L. Your result is compared against a lab reference range that differs slightly for men and women.

Ranges vary between labs, so compare to the range on your own lab report.

What ALT measures

ALT is an enzyme concentrated inside your liver cells, where it helps process amino acids. When those cells are inflamed or damaged, ALT leaks into your bloodstream, so a higher blood level acts as a sensitive marker of liver cell injury.

What high or low levels mean

A high ALT most often reflects fatty liver disease, but it can also point to viral hepatitis, heavy alcohol use, or medications and supplements that stress the liver. Intense exercise or muscle injury can nudge the number up too, since some ALT sits in muscle tissue. A low ALT is usually not a concern and rarely signals disease. Because ALT rarely tells the whole story alone, your clinician reads it alongside AST and the rest of your liver panel. If your result stays elevated on repeat testing, or comes with jaundice, dark urine, or abdominal pain, follow up with a clinician.

ALT FAQ

What does it mean if my ALT is slightly high?

A mildly raised ALT is common and often reflects fatty liver, recent alcohol, a new medication, or hard exercise before the test. Your clinician may simply repeat the test to see whether it settles.

Can I lower my ALT naturally?

Often yes. Losing excess weight, limiting alcohol, staying active, and reviewing any liver-stressing supplements with your clinician can bring a metabolically driven ALT back toward your normal range over weeks to months.

Is a low ALT something to worry about?

Usually not. A low ALT is generally treated as normal variation, and on its own it is not considered a sign of liver disease.

Read alongside your aspartate aminotransferase, alkaline phosphatase, and total bilirubin results to see the fuller picture of liver health.

Sources

• Mayo Clinic Laboratories. Alanine Aminotransferase (ALT), Serum: reference values.

• Cleveland Clinic. Alanine Transaminase (ALT) Blood Test.