What it measures
Alkaline phosphatase (ALP) is an enzyme found mostly in the liver and bones, with smaller amounts from the gut and, in pregnancy, the placenta. The blood level rises when bile flow is blocked or when bone is growing or being remodelled.
Why people test it
- Part of a routine liver function test, mainly as a sign of problems with bile flow.
- Measured when a bone condition is suspected, as faster bone turnover raises ALP.
- Naturally higher in children and teenagers while they grow, and in pregnancy.
- Used to monitor some long-term medicines that can affect the liver.
Typical range
Ranges vary between labs with the method used, age and sex, and your report shows the lab's own range. One NHS trust's lab uses 30 to 130 U/L for adults, with much higher ranges for children and teenagers. Source: Leeds Teaching Hospitals NHS Trust: Blood Sciences Reference Range Database v3.20.
Finger-prick or vein?
A finger-prick sample is usually fine for ALP.