Alkaline Phosphatase (ALP)
Alkaline phosphatase (ALP) is an enzyme found in several tissues, most notably the liver and bones, and also the intestines and placenta. Its level in the blood reflects activity in these areas.
ALP is a helpful marker for both liver and bone health. In the liver, it is especially linked to the bile ducts, so it can flag issues with bile flow. In bone, it reflects the activity of bone-building cells, which is why it naturally runs higher during growth and healing.
Higher ALP can point toward bile duct or liver conditions, or toward increased bone activity. It is normally elevated during childhood growth, pregnancy, and bone healing. Because ALP comes from more than one source, additional tests are often used to work out where it is coming from before drawing conclusions.
A low ALP is uncommon and usually not a concern, though occasionally it can relate to nutritional or rarer factors. It is generally interpreted in context rather than in isolation.
Results are compared to your lab's reference range, which shifts with age and life stage. Because ALP reflects both liver and bone, your clinician will consider your circumstances when interpreting it.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.