ALT (Alanine Aminotransferase)

Alanine Aminotransferase is an indicator of damage to hepatocytes. It is also found in the kidney and in cardiac and skeletal muscle. ALT is present in hepatocyte cytosol with higher concentrations in periportal cells. The magnitude of ALT in serum correlates to the number of hepatocytes affected but cannot be used to assess prognosis. Some animals with severe liver disease may have normal serum ALT due to a lack of viable hepatocytes. Half-life in dogs controversial but levels usually rise rapidly within 24-48 hours and resolve over 2-3 weeks if there is no further liver injury, but the pattern is highly variable. Increases in ALT are seen with phenobarbital treatment. Major differentials for ALT increase include circulatory disturbances (including hepatocellular hypoxia secondary to anaemia), hepatotoxicity, infection, inflammation, endocrine associated hepatopathy, neoplasia, and drug effects.


Dog, Cat


Plasma or Serum


Gel / Plain tube

Collection protocol:

Fasted sample preferred.


Reference(s): Center, S.A. Interpretation of Liver Enzymes. In: Veterinary Clinics of North America Small Animal Practice 37:2 March 2007  p 297 – 333. Stockham, S.L and Scott, M.A. Fundamentals of Veterinary Clinical Pathology 2nd Edition 2008