Alkaline Phosphatase (ALP) Test
A blood test that measures the level of alkaline phosphatase (ALP), an enzyme found in your liver, bones, and other tissues, to help your doctor diagnose and monitor liver or bone disorders.
{"ALP is an enzyme mainly produced in the liver and bones","High ALP levels may indicate liver disease, bone disorders, or gallbladder problems","The test is often part of a routine liver function panel","Abnormal results typically require follow-up testing for diagnosis","Fasting is usually not required, but follow your doctor's instructions"}
Key facts at a glance
- LOINC
- 1783-0
- Short code
- ALP
- Synonyms
- ALP Bld-cCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Serum separator tube (SST/Gold top) or plain red top tube
- Units
- not specified
- Ref low
- 44
- Ref high
- 147
- Critical range
- 20 not specified – 500 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–120 years
- Method
- Spectrophotometric colorimetric assay using para-nitrophenyl phosphate (pNPP) substrate
- CPT
- 84075
- SNOMED
- 271510001
- Specimen volume
- 3-5 mL of whole blood
- Stability
- Room temperature: 2-3 days; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 1 month. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 1–24 hours
- Order
- routine
What is this test?
The Alkaline Phosphatase (ALP) test measures the amount of this enzyme in your blood. Alkaline phosphatase is produced by various tissues in your body, including the liver, bones, kidneys, and intestines. When tissues are damaged or diseased, they release more ALP into your bloodstream, which can be detected through this blood test.
Why is it performed?
Your doctor may order an ALP test as part of a routine health checkup or if you have symptoms such as jaundice (yellowing of skin or eyes), abdominal pain, nausea, or bone pain. It helps evaluate liver function, detect liver diseases like hepatitis or cirrhosis, identify bone disorders such as Paget's disease or osteomalacia, and monitor the effectiveness of treatments for liver or bone conditions.
How is it done?
A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The procedure takes only a few minutes and is generally safe. You may experience slight bruising or soreness at the injection site, which typically resolves quickly. In most cases, you do not need to fast before the test, but always follow your doctor's specific instructions.
Understanding your results
Normal ALP levels vary depending on age, sex, and blood type. Generally, adult values range from 20 to 140 U/L (units per liter), though reference ranges differ between laboratories. High ALP levels may indicate liver problems (hepatitis, cirrhosis, gallstones), bone diseases (Paget's disease, osteomalacia, bone tumors), or other conditions. Low ALP levels are less common but can occur in malnutrition, zinc deficiency, or certain genetic disorders. Your doctor will interpret your results based on your overall health and other test findings.
Reference range
44-147 U/Lnot specified
No special preparation or fasting required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The ALP test is primarily used to assess liver and bone health. Elevated ALP is one of the earliest indicators of liver damage and can help distinguish between liver and bone causes of symptoms. Along with other liver enzymes (ALT, AST, GGT, bilirubin), ALP helps create a complete picture of liver function. In bone disorders, ALP levels correlate with bone formation activity, making it useful for monitoring conditions like Paget's disease or evaluating the effectiveness of osteoporosis treatment. The test is also valuable for detecting biliary obstruction and monitoring patients taking medications that may affect liver function.
Frequently asked questions
Do I need to fast before the ALP test?
What can cause high ALP levels besides liver or bone disease?
Is the ALP test dangerous?
What happens if my ALP levels are abnormal?
Can medications affect my ALP results?
Sources
- 1
- 2
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 10, 2026. · Read our editorial policy