The ALT test checks the level of alanine aminotransferase in the blood to see if the liver is healthy. Elevated levels of the enzyme could indicate damage caused by trauma or a disease process, such as cirrhosis or a strain of hepatitis, as stated by WebMD.
The test is also performed on patients with jaundice, a yellowing of the skin and eyes. An elevated ALT level along with a high bilirubin level suggests the discoloration is caused by liver dysfunction. Otherwise, it could indicate a blood disorder.
The ALT test is used in conjunction with other blood tests to diagnose problems with the liver. These include checking the blood enzyme levels of lactate dehydrogenase, aspartate aminotransferase and alkaline phosphatase.