Causes of elevated alkaline phosphatase include liver injury, bile duct injury, cholestasis, and tumors. Alkaline phosphatase is mainly found in the bile duct epithelium, and elevated alkaline phosphatase reflects liver injury involving the bile ducts or due to obstruction of the bile ducts and biliary stasis. The main causes of bile duct obstruction and liver injury include certain medications, alcoholic liver disease due to long-term alcohol consumption, bile duct stones, bile duct inflammation, and bile duct tumors that block the bile ducts and increase alkaline phosphatase in the blood. In addition, certain neoplastic diseases may be combined with abnormal elevation of alkaline phosphatase.