ALT

Alanine aminotransferase (ALT) is an enzyme concentrated in liver cells. When liver cells are stressed or damaged, ALT leaks into the blood, making it the most liver-specific of the common liver tests.

ALT is a first-line signal of liver injury, and in modern practice the most common reason for a mildly elevated ALT is metabolic dysfunction–associated steatotic liver disease (MASLD, formerly NAFLD) — a marker of broader cardiometabolic health.

1. 1

   FoundationMetabolic HealthThe best place to understand the major drivers of metabolic disease.
2. 2

   ConditionMASLD / MASHMetabolic fatty liver disease
3. 3

   Signal RecordOmega-3 Fatty AcidsFish Oil / EPA + DHA
4. 4

   Body SystemMetabolismEnergy, blood sugar, and how the body processes fuel.

1. Measure it
2. Understand your result
3. See what raises and lowers it
4. Apply evidence-based interventions
5. Recheck on your review cadence

An orientation to how this topic is typically approached — not medical advice.

A persistently elevated ALT (especially ALT > AST) most often reflects fatty liver from insulin resistance and excess weight, but medications, alcohol, and viral hepatitis are also considered. Marked elevations warrant prompt evaluation.

• Part of a liver panel (LFTs)
• Interpreted with AST, GGT, and the AST:ALT ratio

ALT is a validated, first-line marker of hepatocellular injury; the debate over optimal upper limits reflects its sensitivity for early metabolic liver disease.

• AASLD guidance on liver chemistries and MASLD
• ACG clinical guideline on abnormal liver tests

Sources are named authoritative guidelines and scientific bodies. Biomarker pages present established clinical context; calibrated evidence verdicts on specific interventions live in the linked Signal Records.