ALP
Alkaline Phosphatase
What this test measures
ALP is an enzyme found in your liver, bones, and other tissues. This test can help check for liver or bone problems. ALP is naturally higher in children and teenagers whose bones are still growing.
Understanding the numbers
Typical range: Adults: 30-130 U/L
Higher levels are normal in children, teenagers, and during pregnancy.
- Low: 0–30 U/L
- Normal (adult): 30–130 U/L
- Mildly raised: 130–300 U/L
- Markedly raised: 300–600 U/L
Key numbers
- 130 U/L — Adult upper limit
- 300 U/L — Marked rise — investigate liver or bone
Typical UK adult reference range. ALP is naturally higher in growing children, adolescents and pregnancy (placenta makes ALP). A raised ALP needs to be separated into liver vs bone — GGT tests this: if GGT is also raised, ALP is liver; if GGT is normal, ALP is usually bone.
Ranges can vary slightly between laboratories — your report may show slightly different numbers. This page does not read or interpret your result; your GP looks at it alongside your history and other tests.
What a higher-than-normal result can mean
- Could suggest a liver or bile duct problem
- May indicate a bone condition
- Normal to be high during pregnancy and in growing children
- Your GP may do more tests to find the cause
Questions you could ask your GP
- Is my raised ALP coming from my liver or my bones?
- Do I need further tests such as a liver ultrasound or bone scan?
- Could this be related to any medicines I am taking?
- Should I have my vitamin D levels checked as well?
Example stories
These are made-up examples to show how results are talked about in real appointments. They are not real patients.
Pregnant — raised ALP is normal
Farah was 32 weeks pregnant. Her ALP was 240 U/L but other liver tests were normal.
What the GP said: “The placenta makes ALP, so levels roughly double in late pregnancy. Your other liver tests are normal — this is expected and we don't need to do anything.”
What happened next: Eight weeks after delivery her ALP was 90 U/L.
A raised ALP in pregnancy is normal — the placenta produces ALP. Provided the other liver tests (ALT, GGT, bilirubin) are normal, nothing needs to be done.
Bone ALP — Paget's disease
Geoffrey's ALP was 410, GGT 32 (normal), calcium normal. X-ray of his pelvis showed the thickened, disorganised bone of Paget's disease.
What the GP said: “Your normal GGT tells us this is bone ALP, not liver. The X-ray confirms Paget's disease — a condition where bone is remodelled abnormally. A medicine called a bisphosphonate can help.”
What happened next: Geoffrey had a single IV zoledronate infusion. His ALP fell to 180 over three months and his hip pain improved.
When ALP is up but GGT is normal, think bone. Paget's disease, healing fractures, vitamin D deficiency and bone secondaries all raise ALP. The GGT is the key companion test.
Liver ALP — PBC
Emma had itching and tiredness. ALP 380, GGT 290, AMA (anti-mitochondrial antibody) positive.
What the GP said: “A raised ALP and GGT together, with positive AMA, points to primary biliary cholangitis (PBC) — an autoimmune condition of the small bile ducts. A medicine called urso (ursodeoxycholic acid) slows the disease and settles the itching for most people.”
What happened next: Emma started urso and her ALP fell to 140 over six months; the itching settled.
A raised ALP with raised GGT and no obvious cause warrants liver-focused testing. PBC, bile duct disease and liver cancer can present this way. Modern treatment changes the course for many people.
Adolescent growth spurt — high ALP
Dan's ALP was 320 U/L on a routine check. He had grown 10 cm in the last year. All other liver tests were normal.
What the GP said: “Your bones are growing fast — that's where this ALP is coming from. It's completely normal in teenagers, especially boys at your age. We don't need to do anything.”
Children and adolescents have much higher reference ranges for ALP than adults because their bones are actively growing. The adult range doesn't apply — don't panic about a 'raised' ALP in a growing teenager with no other signs.
Before you act on anything here
This page is general information, written to help you understand — it is not personal medical advice and it cannot tell you what is right for you. Talk to your own GP, pharmacist or nurse about your own health.
- Need help now but it's not an emergency? Call NHS 111 or use 111.nhs.uk.
- Emergency? Call 999 or go to A&E.