Elevated liver enzymes (ALT & AST): what they mean

Lab marker guide · Updated June 2026

Understanding lab results

What ALT and AST measure

ALT (alanine aminotransferase) and AST (aspartate aminotransferase) are enzymes that live mostly inside liver cells. When those cells are stressed or damaged, they leak the enzymes into your bloodstream — so a rise is a general marker of liver irritation.

One important nuance: AST is also found in muscle and red blood cells, so AST can rise from intense exercise or muscle injury, not just the liver. ALT is more liver-specific, which is why the two are read together.

Typical reference ranges

Ranges vary by lab (and some labs have lowered their thresholds), but commonly:

• ALT: ~7–56 U/L
• AST: ~10–40 U/L

Read against the range printed on your report — and note the units, which differ between countries.

What elevated liver enzymes can mean

Common causes of raised ALT/AST include:

• Non-alcoholic fatty liver disease (NAFLD) — very common, tied to metabolic health
• Alcohol intake
• Medications and supplements (including some over-the-counter ones)
• Viral hepatitis
• Recent intense exercise or muscle injury (more for AST)

Mild elevations are frequent and often reversible — for example, fatty-liver-related elevations can improve with weight and metabolic changes. The pattern (ALT vs AST, how high, and your history) helps point to the cause.

Why the trend matters

A single mildly high reading often just needs repeating — it may normalize. The real signal is the trend: enzymes drifting up over time, or staying elevated across repeat tests, is more meaningful than one flagged value. Tracking them alongside your weight, alcohol, and other metabolic markers turns scattered readings into a story. See how to read your blood test results and tracking lab results over time.

When to talk to a doctor

Persistently or markedly elevated liver enzymes should be evaluated by a clinician, who can review your medications, order follow-up tests, and look for the cause. For more on understanding your panels, browse the rest of the Quanome blog.

Frequently asked questions

What do ALT and AST measure?

ALT and AST are enzymes found mostly in liver cells. When liver cells are stressed or damaged, they leak these enzymes into the blood, so elevated ALT/AST is a general signal of liver irritation. AST is also found in muscle, so it can rise from intense exercise too.

What are normal ALT and AST ranges?

Ranges vary by lab, but ALT is commonly around 7–56 U/L and AST around 10–40 U/L. Some labs have lowered the 'healthy' ALT threshold. Always read against your own lab's range.

What does it mean if my liver enzymes are high?

Common causes include non-alcoholic fatty liver disease (very common), alcohol, certain medications and supplements, viral hepatitis, and — for AST — recent intense exercise or muscle injury. Mild elevations are common and often reversible.

Should I worry about mildly elevated liver enzymes?

A mild, one-off elevation is common and often not serious, but it shouldn't be ignored — it's worth repeating the test and reviewing causes with a clinician. Persistent or marked elevations need proper evaluation.