Alanine aminotransferase (ALT) is an enzyme primarily found in the liver, though it is also present in smaller amounts in tissues such as the kidneys, heart, and muscles. Since the liver performs many critical bodily functions, diseases that damage liver cells can affect ALT levels. Therefore, the ALT test is widely used to assess liver damage and aid in the diagnosis of liver diseases. When the liver is damaged due to various causes, it releases more ALT enzymes into the bloodstream, leading to elevated serum ALT levels. High ALT levels are considered an indicator of liver damage or disease.

While elevated ALT levels suggest liver damage, low ALT levels within the normal range, as detected in blood tests, generally hold no clinical significance and do not require concern. However, in cases of very advanced liver failure or complete loss of liver function (hepatic failure), significantly low ALT levels can indicate a serious clinical condition and may necessitate urgent medical evaluation and intervention.