Alkaline phosphatase is an enzyme present in many tissues, most abundantly in the bile ducts of the liver and in bone-forming cells. Blood levels reflect the combined output of those two sources, with smaller contributions from the intestine and, in pregnancy, the placenta. It speaks for bile flow and for bone turnover at the same time, which is why it is never read alone.
No readings for this marker yet.
Raised values most often come either from obstructed bile flow, whether inside the liver or in the larger ducts, or from increased bone activity, as in healing fractures, vitamin D deficiency, or Paget disease. A modest rise is normal in pregnancy and marked rises are normal in children and adolescents, whose bones are growing. Low values are uncommon and may accompany an underactive thyroid gland, zinc deficiency, or a rare inherited enzyme deficiency. An out-of-range result is a starting point for a doctor to establish which tissue it came from.
A fatty meal shortly before the draw can raise the number, so the test is usually taken fasting, and blood group and age both influence the baseline. Its source is separated by looking at GGT, which rises with the liver form but not the bone form, and it is interpreted alongside bilirubin, ALT, and AST when a bile duct problem is being considered.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.