Alkaline phosphatase (ALP) is an enzyme that’s found throughout your body. ALP blood tests measure the level of ALP in your blood that comes from your liver and bones, and it’s one of the tests included in a comprehensive metabolic panel. High levels of ALP in your blood may indicate liver disease or certain bone disorders.
Alkaline phosphatase (ALP) is an enzyme that’s found throughout your body. An enzyme is a type of protein in a cell that acts as a catalyst and allows certain bodily processes to happen. There are thousands of enzymes throughout your body that have important functions.
Even though researchers know the function of several other types of enzymes and have studied alkaline phosphatase for decades, they don’t yet know the exact function of ALP. However, researchers believe it’s important for multiple different processes.
Abnormal levels of ALP in your blood can reflect damage to tissue or disruption of normal bodily processes.
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An alkaline phosphatase (ALP) test measures the amount of ALP in your blood. Although ALP exists throughout your body, the two main sources of ALP in your blood are your liver and bones. High levels of ALP may indicate liver disease or certain bone disorders, but an ALP test alone cannot diagnose a condition.
There are two main types of alkaline phosphatase (ALP) blood tests: a general ALP (the more common test) and an ALP isoenzyme test.
A general ALP test is usually included in a blood test known as a comprehensive metabolic panel (CMP) and a liver panel (HFP or LFT).
Whereas an ALP test just measures the level of ALP in your blood, an ALP isoenzyme test can differentiate between types of alkaline phosphatase based on where they originated in your body.
Your healthcare provider may have you undergo an ALP isoenzyme test as a follow-up if you had an abnormal ALP level on a previous test. While an isoenzyme test can provide more detailed information, it’s more technically challenging and expensive, and some laboratories may not offer it.
Your provider may order an alkaline phosphatase (ALP) blood test to help screen for, monitor or help diagnose liver and biliary diseases, bone disorders and other health conditions.
Screening means checking for potential health issues before you experience symptoms. An ALP test is often included in a comprehensive metabolic panel (CMP) and liver panel. Healthcare providers often use these panels as part of a routine check-up to screen for a wide range of potential health problems.
If you have a liver or bone condition or another type of condition, your provider may order an ALP test, often as part of a panel, to monitor your condition to see if it’s improving, worsening or staying the same with or without treatment.
Your provider may use an ALP test for diagnostic purposes when you have signs of possible liver or bone problems. An ALP test can also help diagnose the cause of more general symptoms, such as fatigue, when it’s included in a liver panel or CMP. While providers can’t diagnose a condition based solely on ALP levels, it can be an important part of the diagnostic process. The degree to which the ALP level is elevated or lower than usual may indicate the type or severity of a condition.
Signs and symptoms of liver disease include:
Signs and symptoms of bone disorders include:
A panel blood test involves more than one measurement from a blood sample. Because of this, a liver panel or comprehensive metabolic panel (CMP) provides more information than a test for just alkaline phosphatase. While you can undergo a blood test that just measures your ALP, it’s most often included in a panel with other measurements, such as liver enzymes, to get a more complete picture of your liver’s health.
A healthcare provider called a phlebotomist usually performs blood draws, including those for an ALP blood test, but any healthcare provider who is trained in drawing blood can perform this task. The samples are sent to a lab where a medical laboratory scientist prepares the samples and performs the test on machines known as analyzers.
If your alkaline phosphatase (ALP) test is part of a comprehensive metabolic panel (CMP), you’ll likely need to fast for 10 to 12 hours before your CMP blood test. Fasting means not eating or drinking anything other than water.
In any case, your healthcare provider will give you specific instructions when they order a blood test for you. Be sure to follow them.
You can expect to experience the following during a blood test, or blood draw:
The entire procedure usually takes less than five minutes.
After a healthcare provider has collected your blood sample, they’ll send it to a laboratory for testing. Once the test results are back, your healthcare provider will share the results with you.
Blood tests are a very common and essential part of medical testing and screening. There’s very little risk to having blood tests. You may have slight tenderness or a bruise at the site of the blood draw, but this usually resolves quickly.
In most cases, you should have your test results within one to two business days, though it could take longer.
Blood test reports, including alkaline phosphatase (ALP) test reports, usually provide the following information:
The normal range for alkaline phosphatase (ALP) varies from laboratory to laboratory. One common reference range is from 44 to 147 international units per liter (IU/L), but some organizations recommend a range of 30 to 120 IU/L. Because of this, it’s important to check your test result report to see what your specific lab’s reference range is.
It’s also important to note that normal alkaline phosphatase levels vary with age and sex. ALP levels are typically elevated during childhood and puberty due to bone growth and development. Between the ages of 15 to 50 years, ALP levels are slightly higher in males than females. ALP levels then rise again in old age.
ALP levels may also be higher in pregnant people since ALP exists in the placenta and in people who are healing from a bone fracture (break).
It’s important to note that elevated levels of ALP can range in severity. While a very high ALP level often means you have liver damage or a bone disorder, mildly elevated levels can be caused by many different factors — not necessarily a medical condition that needs treatment. If you only have a mild elevation in your ALP levels, your healthcare provider will likely not have you undergo extensive evaluation. Instead, they’ll likely monitor your levels over time to make sure they don’t get worse.
High alkaline phosphatase (ALP) levels may indicate that there’s damage to your liver or that you have a type of bone disorder. Liver damage creates a different type of ALP than bone disorders do. If your test results reveal that you have high ALP levels, your provider may have you undergo additional tests, such as an ALP isoenzyme test, to determine where the excess ALP is coming from.
High alkaline phosphatase levels in the liver may indicate the following conditions:
High bone alkaline phosphatase levels may indicate the following conditions:
A high level of ALP may also be a sign of untreated celiac disease.
Having an abnormally low level of alkaline phosphatase (ALP) is less common than having an elevated level. It may indicate the following conditions:
If your ALP test result is high or low, it doesn't necessarily mean that you have a medical condition that needs treatment. Other factors can affect your levels, including:
Before determining if you need to undergo further tests, your healthcare provider will take into consideration many aspects of your health and situation, including:
If you’re experiencing symptoms of liver damage, such as jaundice, or bone disorders, such as bone or joint pain, call your healthcare provider. If you’ve been diagnosed with a liver condition or a bone disorder and are experiencing new or concerning symptoms, contact your provider.
If you have any questions about you’re alkaline phosphatase results, don’t be afraid to ask your provider questions.
A note from Cleveland Clinic
Seeing an abnormal test result can be stressful. Know that having a high or low level of alkaline phosphatase doesn’t necessarily mean you have a medical condition and need treatment. Approximately one in 20 healthy people have test results outside of the normal range. Your healthcare provider will let you know if you need to undergo further tests to determine the cause of the abnormal level. Don’t be afraid to ask your provider questions. They’re there to help you.
Last reviewed by a Cleveland Clinic medical professional on 11/04/2021.
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