Liver and bone markers
ALP Levels by Age: What Is a Normal Alkaline Phosphatase Range?
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20268 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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UK labs use one ALP range for every adult: 30 to 130 U/L from age 18. Below 18 the bands run far higher. A boy of 14 can sit near 471 U/L and be entirely normal, because growing bone makes ALP. In adults ALP does drift up with age, but no UK lab adjusts for it.
Not sure which markers you need? Build your test →Your result says ALP 148. The range printed beside it stops at 130. There is a small asterisk, no explanation, and a three week wait to ask anyone about it. So you search, and the first chart you find was written for a different country.
This guide gives you the UK numbers by age, in one place. It also explains the part most charts skip: ALP comes from two places in your body, and knowing which one is the whole question.
1. What is a normal ALP level in the UK?
For adults, 30 to 130 U/L. ALP is short for alkaline phosphatase. It is an enzyme, which means it is a protein that speeds up a chemical reaction. Your blood always carries some. The question is never whether you have any. It is how much, and where it came from.
| Your ALP | What it usually means |
|---|---|
| Below 30 U/L | Low. Usually nothing. Mention it if it repeats. |
| 30 to 130 U/L | Normal. 130 itself is still inside the range. |
| Just over 130, such as 140 or 150 | Mildly raised. Common, and often a one-off. Read it beside ALT and repeat it. |
| Well above 130, or rising | Worth a GP visit, with ALT, calcium and vitamin D beside it. |
Under 18, none of those rows apply. Children and teenagers have their own, much higher bands, shown in section 2.
That last part is the bit charts leave out. Leeds Teaching Hospitals NHS Trust puts it plainly in its pathology handbook:
“ALP is present as several isoenzymes; liver, bone, placenta, intestines and kidney.”
Leeds Teaching Hospitals NHS Trust, pathology test handbook
Isoenzymes are different versions of the same enzyme. Your liver makes one. Your bones make another. A standard result adds them together and reports one number. That is why a raised ALP on its own says very little until you know the source.
What does an ALP of 130, 148 or 170 mean?
Most people arrive holding one figure. Here it is, one adult value at a time. These apply from 18 upward only.
| Your reading | Label | How to read it |
|---|---|---|
| 25 | Low | Under the floor. Rarely acted on alone. Mention a repeat. |
| 80 | Normal | Mid-range. Nothing to do. |
| 130 | Normal | On the top line, not past it. Your lab will not flag it. |
| 140 | Mildly raised | Just over. Read ALT beside it, see what a raised ALP points to, and repeat in a few weeks. |
| 148 | Mildly raised | Still the commonest kind of raised ALP. Same pairing applies. |
| 170 | Raised | Worth a GP conversation, with ALT, calcium and vitamin D. |
| Above 260 | Clearly raised | Twice the top of the range. See a GP rather than waiting. |
One caveat on the whole table. A number is only half the picture with ALP, because the same figure means different things depending on whether it came from your liver or your bones. Section 5 covers how a qualified clinician tells those apart.
2. ALP reference ranges by age
ALP is one of the few blood markers where age genuinely changes the range a lab prints. Below are the bands used by Leeds Teaching Hospitals NHS Trust. Other UK labs sit close to these, though the exact figures shift a little between analysers.
| Age | Female | Male |
|---|---|---|
| Under 14 days | 82 to 249 | 82 to 249 |
| 15 days to 1 year | 122 to 473 | 122 to 473 |
| 1 to 10 years | 142 to 336 | 142 to 336 |
| 10 to 13 years | 128 to 420 | 128 to 420 |
| 13 to 15 years | 55 to 255 | 115 to 471 |
| 15 to 17 years | 49 to 116 | 81 to 333 |
| 17 to 18 years | 43 to 86 | 53 to 149 |
| 18 and over | 30 to 130 | 30 to 130 |
Read down the male column and the shape jumps out. The top of the range peaks at 473 in infancy, stays high through primary school, climbs again at 13, then collapses to 130 by adulthood. Nothing has gone wrong. That curve is a skeleton being built and then finished.
3. Why do children and teenagers run so high?
Because growing bone makes ALP. The cells that lay down new bone are called osteoblasts, and they release alkaline phosphatase as they work. More building means more enzyme in the blood. That bone link is also why ALP turns up on the NHS baseline bone workup.
So ALP tracks growth almost like a speedometer. It runs high in babies, high again through the growth spurt, and settles once the growth plates close. Girls finish that spurt earlier than boys, which is why the 13 to 15 bands split by sex so sharply.
This is the single most common false alarm with ALP. A parent sees a teenager's 300 against an adult chart and panics. Against the right band it is unremarkable.
Age is only half of it. Our guide to a high ALP with normal liver function covers what a raised ALP means when the ALT beside it is fine.
4. Does ALP rise with age in adults?
Yes, it drifts up. No, your lab will not adjust for it. From 18 onwards you are measured against one flat band, 30 to 130 U/L, whether you are 19 or 79. So the drift is real and invisible on your printout.
The clearest evidence comes from a 2015 study in Aging Clinical and Experimental Research, which measured ALP in 626 women after the menopause. Its finding was blunt.
“The ALP levels of people in their 80s were significantly higher than those of people in their 60s.”
— Aging Clinical and Experimental Research, 2015
The same study found the cause. It was not the liver. Bone turnover explained nearly all of it, and treating the women for osteoporosis brought the raised ALP back into range. One caveat: every woman in that study was already being treated for thin bones, so it is not a picture of the general population.
What that means for you is simple enough. A reading in the 120s at 70 is a different thing from the same 120s at 25, and your lab prints them identically. Age is context your result sheet does not give you.
That is unlike eGFR, where your age sits inside the calculation itself. With ALP you get the raw measurement and nothing else.
Two other adult situations push ALP up without anything being wrong. Pregnancy is one, because the placenta makes its own version of the enzyme. Healing a broken bone is the other. Both settle on their own.
5. What does a high ALP point to?
Liver or bone. That is the fork, and everything else follows from it. A blood test measures the enzyme. It does not tell you which tissue sent it.
Clinicians work it out by looking at what sits beside it. This is why ALP is almost never worth measuring on its own:
- A raised ALP with a raised ALT usually points towards the liver.
- A raised ALP with normal liver enzymes points towards bone.
- Calcium and vitamin D help separate the bone causes from each other.
- A repeat test after a few weeks separates a blip from a trend.
A single mildly raised ALP is common and often means nothing. A result that stays up, or one paired with itching, pale stools or yellowing skin, needs a GP appointment rather than a search engine.
None of this is a diagnosis. It is how a qualified clinician narrows the question down. The full liver function panel explains how these markers are read together.
6. What does a low ALP mean?
Far less attention goes here, and a slightly low ALP is usually nothing. It is a normal finding in plenty of healthy people.
A persistently low result can occasionally reflect low zinc or magnesium, since the enzyme needs both to function. It is also seen in some thyroid patterns. Those are prompts to look wider, not answers in themselves.
If your ALP has been below range on more than one test, mention it to your GP rather than treating it yourself.
7. Which blood test includes ALP?
ALP sits on most standard liver panels, so an NHS liver test will include it. If you want it privately, look for a panel that carries the markers around it rather than ALP alone.
Helvy's Thyroid & Vital Organs test measures ALP alongside ALT, albumin, total protein, urea, creatinine and eGFR. That gives you the liver and kidney context in one sample, which is the context a lone ALP is missing. It is a home finger-prick kit, processed by UKAS-accredited UK labs.
If you are not sure which panel fits, the build-my-test tool walks you through it in about a minute.
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See your ALP next to the markers that explain it
Helvy's home blood tests report ALP with plain-English context, so a mildly raised number never sparks a needless panic. Samples are processed by UKAS-accredited UK labs.
Frequently asked questions
What is a normal ALP level by age in the UK?
From 18 onwards, 30 to 130 U/L. Below that, the bands rise steeply. Leeds Teaching Hospitals NHS Trust lists 142 to 336 U/L for ages 1 to 10, and 115 to 471 U/L for boys aged 13 to 15.
Is an ALP of 150 something to worry about?
In an adult it is mildly above the usual 130 ceiling, and that is a common finding. It is a prompt to look again rather than a verdict. A clinician will want your ALT, calcium and vitamin D beside it, and often a repeat test.
Is an ALP of 130 high?
No. In an adult, 130 is the top of the range rather than a step past it, so your lab will report it as normal. It does sit at the edge. If yours has been climbing towards 130 across several tests, the trend is the thing worth mentioning, not the single figure.
What is the normal ALP range for women?
From 18, the same as for men: 30 to 130 U/L. The sexes only split in the early teens, when girls finish their growth spurt sooner. Pregnancy is the main adult exception, and it raises ALP.
Is a normal ALP different at 70 than at 30?
Not on your printout. Every UK adult is measured against 30 to 130 U/L. In real life ALP does climb with age, mostly from bone turnover, and one study found women in their 80s ran higher than women in their 60s. Your lab does not adjust for that.
Why is my teenager's ALP over 300?
Growing bone makes ALP. Through the growth spurt the upper limit for a boy of 13 to 15 reaches 471 U/L. A 300 read against an adult chart looks alarming and against the right band is unremarkable.
Does ALP come from the liver or the bones?
Both, plus the placenta, intestines and kidney. A standard test adds them together into one number. Clinicians work out the source from what sits beside it, mainly ALT for liver and calcium for bone.
Do UK labs adjust ALP for your age?
Only up to 18. Paediatric samples are reported against age and sex bands. After that everyone is compared with the same 30 to 130 range, however old they are.
Can pregnancy raise your ALP?
Yes. The placenta makes its own version of the enzyme, so ALP rises through pregnancy and can sit well above the usual adult ceiling. It settles after birth.
Related guides
ALP Blood Test UK
What the test measures and why it is ordered.
Liver Enzyme Levels by Age
How ALT, AST and GGT shift across the decades.
Full Blood Count UK
The other panel people are handed with no explanation.
Blood Test Reference Ranges UK
Why 'normal' on a lab report is a population range, not a target.