Liver ALP is the isoenzyme of alkaline phosphatase produced specifically by liver cells and the bile duct epithelium. Measuring liver ALP separately from total ALP allows for more precise identification of hepatobiliary disease, particularly when total ALP is elevated and it is unclear whether the source is liver or bone.

Liver ALP is elevated in conditions that impair bile flow (cholestasis), including gallstones, primary biliary cholangitis, sclerosing cholangitis, and drug-induced liver injury. It is also elevated in conditions that infiltrate the liver such as sarcoidosis, lymphoma, and metastatic cancer. It is a useful adjunct when GGT is elevated but the full ALP isoenzyme profile is needed.