Alkaline Phosphatase

A common adult reference range for ALP is about 44-147 U/L, though the exact limits vary by lab and method. ALP comes from both the liver and bone, so the normal range is wider than for the liver-specific transaminases. Healthy growing teenagers and pregnant women normally run higher because of active bone growth and the placenta.

A raised ALP most often points to either the biliary system (bile duct obstruction, gallstones, some liver disease) or to bone turnover (a healing fracture, Paget's disease, or normal adolescent growth). Because it has two main sources, an isolated high ALP is usually followed up by checking GGT: if GGT is also high the source is likely the liver or bile ducts, and if GGT is normal the ALP is more likely bone-derived. Labs can also run ALP isoenzymes to separate the fractions.

That pattern often means the ALP is coming from bone rather than the liver, especially in a growing adolescent, after a fracture, or with a bone condition. A normal GGT alongside the high ALP supports a bone source, while a raised GGT points back to the liver or bile ducts. Your physician may order ALP isoenzymes or imaging if the elevation persists.

Testosterone replacement does not directly raise ALP, so it is not a marker that changes because of TRT itself. A persistent, unexplained elevation should be worked up as it would in anyone else, typically with GGT and liver imaging. Bring an ongoing high ALP to your physician regardless of whether you are on testosterone.