Insight into your alkaline phosphatase.
Alkaline phosphatase is an enzyme with bone and liver as its main sources. The value gives insight into bile drainage and bone metabolism, with personal explanation from our doctors.
Also known as: alkaline phosphatase, ALP, AF, bile ducts, bone
Personal assessment by our BIG-registered Bloodworks® doctors
By the Bloodworks editorial team
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Background
What is alkaline phosphatase?
Alkaline phosphatase (ALP, in Dutch AF) is an enzyme that breaks down phosphate compounds. It is found in several places in the body, with bone and liver as its main sources: in the liver mainly in the cells that line the bile ducts, in bone in the cells that build new bone tissue. Smaller amounts come from the intestine and, during pregnancy, from the placenta. If the drainage of bile stagnates or the bile ducts become irritated, alkaline phosphatase rises in the blood. The value also rises with active bone formation.
A raised alkaline phosphatase therefore does not always fit the liver. In children and adolescents who are growing, a higher value is normal, because bone is being built at full pace. During pregnancy, especially in the last trimester, a rise is also physiological. To judge the source of a rise, a doctor looks at gamma-GT: that enzyme comes from the liver and bile ducts but not from bone. If both are raised, that points towards the bile ducts; if only alkaline phosphatase is raised, the source more likely lies in bone. Alkaline phosphatase also complements the liver tests ALT and AST: those point mainly to irritation of the liver cells themselves, while alkaline phosphatase points more towards bile drainage.
In brief
Bone and liver
The two main sources of this enzyme
Interpret with gamma-GT
Together with gamma-GT the source is easier to judge
Growth and pregnancy
A higher value is then usual
Complements ALT/AST
Points more towards the drainage of bile
This marker is also included in
Testing several values in a single draw takes one blood collection and gives a more complete picture. The choice is yours.
Common reasons to test
When can insight into your Alkaline phosphatase be valuable?
Below are some situations in which measuring Alkaline phosphatase can provide insight.
Insight into your bile duct values
Alkaline phosphatase assesses the drainage of bile and complements the liver tests ALT and AST.
With a raised liver value
If your ALT or AST is raised, alkaline phosphatase helps determine whether the bile ducts also play a role.
With questions about bone metabolism
Alkaline phosphatase also comes from bone. The value is therefore sometimes taken into account with questions about bone metabolism.
Together with gamma-GT
The combination with gamma-GT helps the doctor judge whether a rise comes from the bile ducts or elsewhere.
Tracking a value over time
For alkaline phosphatase the development over time is often more informative than a single measurement. Re-testing makes a change visible.
What your result means
Alkaline phosphatase too high or too low: what does your result mean?
Alkaline phosphatase is measured in units per litre (U/L). There is no single fixed normal value: the laboratory that tests your blood states the reference values that apply there alongside your result, and these depend among other things on age. Important: growth in young people, pregnancy and bone metabolism influence this value.
A low value
A low alkaline phosphatase is uncommon and often harmless. A doctor considers, for example, a prolonged shortage of certain nutrients such as zinc or magnesium, an underactive thyroid or, rarely, a hereditary cause. Our doctor provides explanation and context with your result.
A normal value
A value within the laboratory's reference values gives a reassuring picture of bile drainage at this moment. It remains a snapshot. The doctor always assesses your value together with your symptoms and your other liver values.
An elevated value
A raised alkaline phosphatase can come from the liver and bile ducts or from bone. A doctor first considers whether there is a physiological explanation: growth in children and adolescents and pregnancy raise the value in a normal way. The doctor then looks at the bile duct side, for example obstructed bile drainage due to gallstones, fatty liver or medication use, and at the bone side, such as increased bone formation after a fracture or a bone condition that needs further investigation. The combination with gamma-GT helps interpret the origin. A single measurement is not a diagnosis. Our doctor explains what your value means and whether re-testing or follow-up via your GP is customary.
How we interpret your result
Our doctors interpret your alkaline phosphatase against the laboratory's reference values and your personal context, such as age, pregnancy, medication use and any known conditions.
Related tests
Often combined with Alkaline phosphatase.
A single marker gives one perspective. For a broader picture you can combine Alkaline phosphatase with a theme package or related markers.
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Frequently asked questions
Everything you want to know
Do I need to fast for this test?
No, you do not need to fast for alkaline phosphatase. If you are also measuring glucose or cholesterol at the same time, fasting is customary.
What does ALP mean in my blood results?
ALP stands for alkaline phosphatase, in Dutch abbreviated as AF. It is an enzyme that comes mainly from bone and from the liver and bile ducts. The value is used to assess bile drainage and bone metabolism.
What is a normal alkaline phosphatase value?
That differs per laboratory and depends among other things on your age. Children and adolescents who are growing naturally have higher values, and the value is also higher during pregnancy. The laboratory therefore states the reference values that apply to you alongside your result; those are leading.
What can a low alkaline phosphatase mean?
A low value is uncommon and often harmless. A doctor considers, for example, a prolonged shortage of nutrients such as zinc or magnesium, an underactive thyroid or, rarely, a hereditary cause. Our doctor provides explanation and context with your result.
What does it mean if only my alkaline phosphatase is raised?
Alkaline phosphatase also comes from bone. If only this value is raised and your gamma-GT is not, the source may lie in bone metabolism rather than in the bile ducts. During pregnancy and in periods of growth a higher value is also usual.
Why is alkaline phosphatase often measured together with gamma-GT?
Gamma-GT comes mainly from the bile ducts and not from bone. If both enzymes are raised, that points towards the bile ducts. If only alkaline phosphatase is raised, the source may lie elsewhere. The combination helps the doctor interpret the origin.
What is the difference between alkaline phosphatase and ALT or AST?
ALT and AST are found mainly in the liver cells and rise with irritation or damage to those cells. Alkaline phosphatase comes mainly from the cells around the bile ducts (and from bone) and points more towards the drainage of bile. They therefore complement each other.
Is a higher value during pregnancy or growth normal?
Yes. During pregnancy and in periods of growth a higher alkaline phosphatase is usual, because the enzyme is also involved in bone metabolism. The doctor takes this into account in the interpretation.
Can a single elevated value already mean a problem?
No. A single measurement is not a diagnosis. The doctor looks at your alkaline phosphatase together with your gamma-GT, your other liver values and your context, and advises whether re-testing or follow-up is useful.
What do I do with my result?
You receive a PDF report with your value and personal explanation. What you do with it, such as discussing it with your GP, remains entirely your choice.
Is it 'alkalische fosfatase' or 'alkalisch fosfatase'?
Both spellings occur in Dutch. Alkalische fosfatase is the usual form, and alkalisch fosfatase is also used and means exactly the same. In English the enzyme is called alkaline phosphatase. On your result you usually see the abbreviation AF, internationally ALP.
What is the difference between alkaline phosphatase and phosphate?
Alkaline phosphatase is an enzyme that breaks down phosphate compounds. Phosphate is the mineral itself, which can be measured in the blood as a separate determination. They therefore say different things: the enzyme points mainly towards bile drainage and bone metabolism, while the mineral belongs to the mineral balance. The laboratory states the reference values that apply there alongside both determinations.
Can I do anything myself about a raised alkaline phosphatase?
That depends on the cause, and a single determination does not yet establish it. In young people who are growing and during pregnancy a higher value is usual. If the source lies in the liver and bile ducts, factors such as alcohol, fatty liver or medication use can play a part. If the rise comes from bone, that is an entirely different track. Never adjust your medication on your own initiative. Our doctor explains what your value means and whether re-testing or follow-up via your GP is customary.
In the Health Guide
Read more about this value
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