Summary: Alanine transaminase (ALT) also known as alanine aminotransferase or (sGPT) is a metabolic enzyme expressed primarily in the liver. Elevation of ALT levels is an indication of liver damage and has been associated with liver injury. ALT levels are monitored routinely in patients with liver diseases. ALT is also a very useful tool for preclinical investigation of experimental drug formulations and ALT levels are commonly used to monitor and attenuate the hepatotoxic effects of experimental drugs in rodents.