[3] ALT catalyzes the transfer of an amino group from L-alanine to α-ketoglutarate, the products of this reversible transamination reaction being pyruvate and L-glutamate.

[5] ALT is commonly measured clinically as part of liver function tests and is a component of the AST/ALT ratio.

[9] When elevated ALT levels are found in the blood, the possible underlying causes can be further narrowed down by measuring other enzymes.

For example, elevated ALT levels due to hepatocyte damage can be distinguished from bile duct problems by measuring alkaline phosphatase.

The intent was to identify donors potentially infected with hepatitis C because no specific test for that disease was available at the time.

With the introduction of second-generation ELISA antibody tests for hepatitis C, the Red Cross changed the ALT policy.