Liver function
ALP blood test
An ALP (alkaline phosphatase) blood test measures an enzyme found mainly in your liver and bones, and it forms part of a standard liver function test. A raised ALP can point to the liver (especially the bile ducts) or to increased bone activity, so it is interpreted alongside other markers such as GGT to work out where it's coming from.
- What it measures
- Alkaline phosphatase, an enzyme from the liver and bones
- Sample
- Venous blood sample
- Fasting
- Not required
- Also known as
- alkaline phosphatase
- Included in 57 Health tests
- 8 panels, from £95
ALP reference range
Guide only| Category | Guide range |
|---|---|
| Adults | 30–130 U/L |
ALP comes mainly from the liver and bone, so it is naturally higher in growing children and teenagers and in pregnancy (from the placenta), which is normal. GGT is usually checked alongside to tell whether a raised ALP is from the liver or from bone.
These are general UK adult guide ranges from public health sources, shown for orientation only. Reference ranges vary by laboratory, assay, age and sex, so your result is always interpreted against the range quoted by the analysing laboratory on your report.
What does a high ALP level mean?
A high ALP points either to the liver (often a blockage or slowing of bile flow, known as cholestasis, such as from a gallstone or bile-duct problem) or to increased bone turnover, such as a healing fracture, vitamin D deficiency or Paget's disease.
It is also naturally raised in adolescence and pregnancy. Because ALP alone can't separate these, a GGT (which rises with liver but not bone causes) is used alongside it to point to the source.
What does a low ALP level mean?
A low ALP is uncommon and usually not a cause for concern.
It can occasionally be linked to malnutrition, low zinc or magnesium, an underactive thyroid, or (rarely) an inherited condition, so it's interpreted in the context of your other results.
When to consider an ALP test
- A general or liver health check
- Jaundice, itching, or upper-abdominal discomfort
- Bone pain or a suspected bone problem
- Monitoring the liver while on certain medicines
- Following up an abnormal previous result
Frequently asked questions
This page is general information about a blood marker and is not medical advice or a diagnosis. An ALP test screens and gives context; results are interpreted by a clinician alongside your symptoms, history and other markers. Always follow the guidance on your own report.