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.
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