Alkaline Phosphatase
An enzyme from the liver's bile ducts and from bone that rises with bile blockage or bone growth.
| Typical reference range | 36–130 U/L |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
Alkaline phosphatase is produced mainly by the liver (bile duct lining) and bone-building cells (osteoblasts), with smaller contributions from the intestine and, in pregnancy, the placenta.
Why it matters
ALP helps detect cholestasis (impaired bile flow) and bone disorders. If ALP is high, a raised GGT points to a liver source, while normal GGT suggests bone.
What a high result can mean
Liver causes include bile duct obstruction (gallstones, tumors), primary biliary cholangitis, primary sclerosing cholangitis and drug-induced cholestasis. Bone causes include growth in adolescents, healing fractures, Paget's disease, vitamin D deficiency/osteomalacia, hyperparathyroidism and bone metastases. Pregnancy raises it normally.
What a low result can mean
Low ALP can occur with zinc or magnesium deficiency, malnutrition, hypothyroidism, Wilson's disease, estrogen therapy and the rare genetic disorder hypophosphatasia.
What affects the result
Values are much higher in children and teenagers. A fatty meal can raise intestinal ALP in people with blood types O and B, so fasting improves consistency. GGT or ALP isoenzymes help locate the source.
Units and conversion
Usually reported in U/L.
- From IU/L: multiply by 1 to get U/L
- From ukat/L: multiply by 60 to get U/L
Also called on lab reports
ALP, Alk Phos, Alk. Phosphatase, Alkaline Phosphatase, Serum, Alkaline Phosphatase, Total
Related tests: Liver
This page is educational and does not replace advice from a healthcare professional.