Alkaline Phosphatase (ALP) Blood Test
A simple blood test that measures the level of alkaline phosphatase (ALP), an enzyme produced mainly by the liver and bones. This test helps your doctor evaluate liver function, detect bile duct blockages or gallstones, and identify bone disorders such as Paget's disease. It is often included in a liver function panel or routine blood work during a general health checkup to support diagnosis and monitor ongoing treatment.
{"ALP is an enzyme primarily made in the liver, bones, and kidneys","High ALP levels may indicate liver disease, bone disorders, or bile duct obstruction","The test is performed on a blood sample (serum)","Normal ranges vary by age and gender","Your doctor will interpret results based on your overall health"}
Key facts at a glance
- LOINC
- 1779-8
- Short code
- ALP
- Synonyms
- ALP Liver SerPl-cCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- not specified
- Ref low
- 40
- Ref high
- 129
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Spectrophotometric enzymatic assay using p-nitrophenyl phosphate (pNPP) substrate
- CPT
- 84075
- SNOMED
- 271511001
- Specimen volume
- 1-2 mL serum minimum
- Stability
- Room temperature: 7 days; Refrigerated (2-8°C): 7-14 days; Frozen (-20°C): 30 days
- 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. ALP is produced mainly by the liver and bones, but also by the intestines, kidneys, and placenta in pregnant women. This test is commonly part of a liver function panel and helps doctors assess liver health and detect bone disorders.
Why is this test performed?
Your healthcare provider may order an ALP test to: evaluate liver function and detect liver damage or disease such as hepatitis or cirrhosis; identify bile duct obstructions or gallstones; diagnose bone disorders including Paget's disease, osteomalacia, or bone tumors; monitor the effectiveness of treatments for liver or bone conditions; or as part of routine blood work during a general health checkup.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The blood is collected in a tube and sent to a laboratory for analysis. You do not need to fast before this test unless specifically instructed by your doctor. The procedure only takes a few minutes and is generally well-tolerated.
Understanding your results
Normal ALP levels vary based on age, gender, and blood type. Generally, adult normal ranges are 20 to 140 IU/L (international units per liter), though this may vary by laboratory. Higher than normal ALP levels may indicate liver disease, bile duct obstruction, gallstones, bone disorders, certain cancers, or heart failure. Lower than normal ALP levels are less common but may indicate malnutrition, zinc deficiency, or certain genetic disorders. Your doctor will interpret your results in context with other liver tests and your overall health condition.
Are there any risks?
The blood draw associated with this test carries minimal risks, including slight bruising, bleeding, or dizziness. These side effects are usually temporary and resolve quickly. There are no known risks from the test itself.
Reference range
40-129 U/Lnot specified
No fasting or special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated ALP is commonly associated with liver conditions such as hepatitis, cirrhosis, or liver tumors; bile duct obstruction from gallstones or strictures; bone diseases including Paget's disease, osteomalacia, or bone metastases; and other conditions like hyperthyroidism, heart failure, or certain infections. Isolated ALP elevation without other liver enzyme changes often points to bone rather than liver involvement. ALP testing is particularly valuable when combined with other liver enzymes (ALT, AST, GGT, bilirubin) to determine the exact nature and origin of liver or bone abnormalities.
Frequently asked questions
Do I need to fast before the ALP test?
What can cause a false high ALP result?
Is a high ALP level always serious?
How is an abnormal ALP result followed up?
Can children have different ALP levels?
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