Alanine aminotransferase (ALT) is an enzyme primarily found in your liver. An enzyme is a protein that helps speed up chemical reactions. ALT is involved in cellular energy production. ALT levels in ...

Liver enzymes are proteins in your liver that speed up chemical reactions. If your liver is damaged, blood tests will show abnormally high levels of these enzymes circulating in your bloodstream.

Mark Gurarie is a writer covering health topics, technology, music, books, and culture. He also teaches health science and research writing at George Washington University's School of Medical and ...