# ALT / AST

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes inside your cells that spill into your blood when liver cells are injured. ALT is fairly liver-specific. AST also comes from muscle, heart, and red blood cells. A rise in these enzymes most often means fatty-liver disease (MASLD), alcohol use, viral hepatitis, or drug toxicity. And the AST/ALT ratio helps tell the causes apart. Persistently raised liver enzymes are tied to higher cardiometabolic risk and higher death from all causes.

## Sources

- McGill MR. (2016). The past and present of serum aminotransferases and the future of liver injury biomarkers. EXCLI Journal. https://doi.org/10.17179/excli2016-800

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_Canonical: https://longevity-switzerland.com/en/glossary/alt-ast · Part of Longevity Cities · Updated 2026-06-22_