Serum alkaline phosphatase is derived predominantly from the liver and bones. An elevated alkaline phosphatase can be fractionated to determine if it originates from the liver or bones. The major value of the serum alkaline phosphatase in the diagnosis of liver disorders is in the recognition of cholestatic disease. However, an elevation in the alkaline phosphatase concentration is a relatively common finding and does not always indicate the presence of hepatobiliary disease. In addition, normal serum values of alkaline phosphatase vary based upon demographic and clinical circumstances.