Clinical investigations from the RACP

Alkaline phosphatase: when to measure it and what to do next

Jeffrey D Zajac, Cherie Chiang



Alkaline phosphatase (ALP) measurement is one of the most widely used and simple biochemical tests, and an extremely useful marker of bone and liver disease. Isolated elevation usually suggests bone disease, and persistent elevation in an adult requires investigation.

Key Points

  • Total serum ALP should be measured in a patient who has symptoms of cholestatic liver disease, bone pain, low bone mineral density (with or without fractures), or general debility.
  • An isolated raised serum ALP level is usually due to increased osteoblast activity.
  • ALP is elevated in several bone conditions. Paget’s disease can result in an increase to more than 10 times normal.
  • If an elevated total ALP is accompanied by an elevated gamma glutamyl transpeptidase (gGT) level then the cause is most likely of liver origin.