High alkaline phosphatase: what it means and what to do

A high alkaline phosphatase means your body is making more of it, usually in the liver or the bones. In pregnancy, in teenagers who are still growing or after a fracture, that is normal. Otherwise GGT helps show where it comes from, and your doctor decides whether more tests are needed.

What high alkaline phosphatase means

Alkaline phosphatase comes mainly from two places: the bile ducts of the liver and the bones. It rises when bile does not flow well, but also when bone renews faster.

The number alone does not say which. That is why it is read with GGT: if GGT is high too, the liver is usually involved. If it is normal, bone is more likely.

What causes high alkaline phosphatase

The first three usually do not mean an illness.

• Pregnancy: In the last months the placenta makes it too. That is normal.
• Growth: In teenagers the bones are getting longer, and the number can be much higher than in adults. That is normal.
• A healing bone: After a fracture it rises for a while, as new bone forms.
• Liver and bile ducts: A stone or a narrowing in the bile ducts, some medicines or a fatty liver can push it up. GGT usually rises too.
• Bone that renews too fast: For example with a severe lack of vitamin D or an overactive thyroid that is not treated. Or with Paget’s disease of bone, a rare condition in which bone renews in a disorganised way.
• Rarer causes: Other liver diseases, or a tumour that affects the bones, liver or bile ducts. That is why a high number with no clear reason needs a doctor’s look.

Symptoms of high alkaline phosphatase

Usually none: a high alkaline phosphatase is found by chance, on a blood test.

If there are symptoms, they come from the cause. If bile is not flowing well, there can be:

• Yellow eyes or skin
• Dark urine
• Pale stools
• Itching

If bone is involved, there can be bone pain. With yellow eyes or skin, dark urine or pale stools, see a doctor today. If you also have a fever or bad pain in your belly, call 112 or go to the emergency department. For itching alone, talking to your doctor is enough.

Liver or bone? How to tell

GGT is a liver enzyme that bone does not have. If alkaline phosphatase and GGT are high together, the cause is usually in the liver or the bile ducts.

If GGT is normal, the alkaline phosphatase more likely comes from bone. Your doctor then looks at calcium and vitamin D, and sometimes asks for bone alkaline phosphatase, a test that measures only the part from bone.

Which tests to read alongside it

These tests help show where it comes from.

What your result means

The upper end of the scale, in U/L. If your report prints different limits, its limits count.

• Within your report’s limits, Women: usually 35 to 104, Men: usually 40 to 129: Normal. Usually fine. It is read together with GGT and the other liver tests. In the Rosa report you also see whether you are in your optimal range.
• Above your report’s limit, Women: usually above 104, Men: usually above 129: High. It can come from the liver or from bone. GGT helps tell which. Show your report to your doctor, with your GGT: they decide whether to repeat the test or do others.

What to do if it is high

It depends on the cause, and your doctor looks for it. Where to start:

• Check GGT, the transaminases and bilirubin on your report.
• Show your report to your doctor, who decides whether to repeat the test or do other checks, such as an ultrasound scan.
• If you are pregnant, or have had a fracture recently, say so: it often explains the number.
• If you take medicines or supplements, bring the list to your doctor, and do not stop anything on your own.
• What to eat: no diet lowers it directly. If a fatty liver is involved, less alcohol, less sugar and more movement help.
• If low vitamin D is involved, your doctor decides the treatment, usually a supplement.

When to worry

Talk to your doctor if:

• It is high together with GGT or the transaminases: talk to them soon.
• It is high with a normal GGT: your bones need looking at.
• It is high and there is no clear reason, such as pregnancy or a fracture.
• You have bone pain that does not go away, or you lose weight for no reason.
• Your eyes or skin are yellow, or you have dark urine or pale stools: see a doctor today. If you also have a fever or bad pain in your belly, call 112 or go to the emergency department.

Frequently asked questions

Can high alkaline phosphatase be a sign of cancer? Usually not: the most common causes are pregnancy, growth, a healing bone, the liver or the bile. A tumour that affects the bones, liver or bile ducts is a rarer cause. That is why, when there is no clear reason, your doctor looks for one with more tests.

High alkaline phosphatase and GGT: what does it mean? Usually that the cause is in the liver or the bile ducts, because bone has no GGT. Bile that does not flow well, some medicines or a fatty liver are often behind it, more rarely other liver diseases. Show your report to your doctor soon, who decides which tests to do.

Slightly high alkaline phosphatase: should I worry? Usually not, if your GGT, transaminases and bilirubin are normal and you feel well. Bone is often behind it, for example after menopause, or a fatty meal before the test. Show your report to your doctor anyway, with no rush.

High alkaline phosphatase in pregnancy: is it normal? Yes, above all in the last months: the placenta makes it too. If you have itching, especially on your hands and feet, talk to your obstetrician soon.

Does low vitamin D raise alkaline phosphatase? Only when the lack is severe and has lasted a long time, which is rare. A slightly low vitamin D, which is very common, usually does not change it.

Sources

• Newsome and colleagues, guidelines on the management of abnormal liver blood tests. Gut, 2018. PMID 29122851
• Riancho, diagnostic approach to patients with low serum alkaline phosphatase. Calcified Tissue International, 2023. PMID 36348061
• Bolland and colleagues, prevalence of biochemical osteomalacia in adults undergoing vitamin D testing. Clinical Endocrinology, 2021. PMID 33866594
• Scappaticcio and colleagues, abnormal liver blood tests in patients with hyperthyroidism: systematic review and meta-analysis. Thyroid, 2021. PMID 33327837
• Day and colleagues, fatty acid chain length and the rise in intestinal alkaline phosphatase after a fatty meal. Annals of Clinical Biochemistry, 1992. PMID 1610103