Alkaline Phosphatase
Reviewed
An alkaline phosphatase (ALP) test measures the amount of ALP in your blood. ALP is an enzyme found in all body tissues, with higher amounts in liver, bile ducts, and bones. Abnormal levels may indicate liver disease, bone disorders, or chronic kidney disease.
Preparation and collection
You usually need to fast (not eat or drink) for several hours before these tests. You may need to stop taking certain medicines before the test, but do not stop unless your provider tells you to.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- The test alone cannot identify the source of elevated ALP (liver vs. bone).
- Higher than normal levels may not indicate a medical condition needing treatment.
- Many factors such as pregnancy, age, medications, and recent meals can affect ALP levels.
- An ALP isoenzyme test to differentiate sources may not be available everywhere.
- Low levels are less common and may require further evaluation.
What to do next
If results are abnormal, your provider may order additional tests such as an ALP isoenzyme test, liver function tests, or other tests to identify the underlying cause. They will consider your symptoms, medical history, and other test results.