ALT (Alanine Aminotransferase) (ALT)

What is ALT?

ALT (alanine aminotransferase) is an enzyme primarily found in liver cells. When liver cells are damaged or inflamed, ALT is released into the bloodstream, making it one of the most specific markers of liver injury or hepatocellular damage.

Why is it Tested?

Doctors order ALT to detect liver damage, monitor liver disease progression, assess medication toxicity, and screen for hepatitis. It’s included in comprehensive metabolic panels and liver function tests as a sensitive indicator of hepatocellular injury.

Normal Ranges

Reference ranges for ALT:

Normal: 7–56 U/L

Some laboratories use gender-specific ranges, with slightly lower upper limits for women. Values may also vary by age and body mass index.

Reference ranges vary by authority. Track yours across multiple standards with automatic unit conversions in LabsVault.

What do Abnormal Results Mean?

Abnormal results are not a diagnosis. Always discuss your results with a qualified healthcare provider before making any medical decisions.

Low ALT

Very low levels are generally not concerning and may indicate:

Normal liver function
Reduced muscle mass
Certain nutritional deficiencies

High ALT

Elevated levels suggest:

Hepatitis (viral, autoimmune, or toxic)
Fatty liver disease
Medication-induced liver injury
Cirrhosis
Muscle damage (less common)
Heart attack (rarely)

How to Track Over Time

ALT levels help monitor liver disease progression and treatment response. Rising trends may indicate worsening liver damage, while decreasing levels suggest healing or effective treatment. Regular monitoring is important for patients on potentially hepatotoxic medications.

ALT (Alanine Aminotransferase)