This site is sponsored by the VHA National Center for Health Promotion and Disease Prevention (NCP) to help Veterans stay well and well-informed..
Labs determine 'normal range' by surveying the people using that lab. For my lab, normal ALT is 6-34 and normal AST is 9-34. ALT is made in the liver so high levels indicate it is being leaked out of damaged liver cells into the bloodstream.
Why the ALT Test Is Performed. The ALT test is used to evaluate whether a patient has liver damage. Liver damage causes an elevation in ALT levels. However, the test does not show how much damage there is or how much fibrosis (scarring) is present.f the liver is damaged or not functioning properly, ALT is released into the blood. This causes ALT levels to increase. The alanine aminotransferase (ALT) test is used to evaluate liver function.