Bone-Specific Alkaline Phosphatase (BSAP)
Bone-specific alkaline phosphatase (BSAP) is a form of the enzyme alkaline phosphatase produced by bone-building cells. Measuring the bone-specific form helps focus on skeletal activity rather than the enzyme from other tissues like the liver.
BSAP is a bone turnover marker that reflects bone formation, and separating it from total alkaline phosphatase makes it more specific to the skeleton. Clinicians use it to help monitor bone health, follow certain bone conditions, and assess response to osteoporosis therapy over time. It is generally read as part of a broader picture rather than in isolation.
A higher BSAP can reflect increased bone-forming activity, which appears in several settings ranging from healing and treatment response to conditions with accelerated bone remodeling. Because the pattern varies by cause, an elevated value is a signal to look at the wider context rather than a diagnosis on its own. Your clinician weighs it against your history and other tests.
A lower BSAP may reflect reduced bone formation and is interpreted alongside your other results. On its own it is rarely meaningful without the fuller clinical picture.
There is no universal target value, and BSAP is most helpful tracked over time and in the context of any bone condition or treatment. Your clinician can interpret your result for you.
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.