Alkaline Phosphatase (ALP) Test
The Alkaline Phosphatase (ALP) test measures the level of an important enzyme found mainly in your liver, bones, intestines, and kidneys. This simple blood test helps your healthcare provider evaluate liver function and bone health, screen for conditions such as bile duct blockages or bone disorders, and monitor how well treatments for liver or bone conditions are working.
{"ALP is an enzyme found mainly in the liver and bones","Elevated ALP may indicate liver disease, bone disorders, or gallstones","The test is often part of routine liver function testing","Results are interpreted alongside other liver enzymes for accuracy","Fasting is usually not required, but follow your doctor's instructions"}
Key facts at a glance
- LOINC
- 49924-4
- Short code
- ALP macro/total ratio
- Synonyms
- ALP macro CFr SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST/gel tube) or plain red top tube
- Units
- not specified
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Kinetic colorimetric assay using p-nitrophenyl phosphate (PNPP) substrate with diethanolamine buffer, measuring macro-alkaline phosphatase fraction relative to total alkaline phosphatase
- CPT
- 84075 (Alkaline phosphatase, total)
- SNOMED
- 31308007
- Specimen volume
- 0.5-1.0 mL of serum minimum
- Stability
- Room temperature: 24-48 hours; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C or below): several weeks to months
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 4–24 hours
- Order
- routine
What is the Alkaline Phosphatase test?
Alkaline Phosphatase (ALP) is an enzyme—a protein that helps speed up chemical reactions in your body. This enzyme is found in many tissues throughout the body, with the highest concentrations in the liver, bones, intestines, and kidneys. The ALP blood test measures the amount of this enzyme in your bloodstream to help healthcare providers assess how well certain organs are functioning.
Why is this test performed?
Your doctor may order an ALP test as part of a routine health checkup or to investigate specific symptoms. It is commonly used to screen for liver diseases such as hepatitis or cirrhosis, to detect bile duct obstructions or gallstones, to evaluate bone disorders including Paget's disease or bone cancer, and to monitor the effectiveness of treatments for liver or bone conditions. The test is often performed together with other liver function tests to get a complete picture of liver health.
How is the test done?
The ALP test is a simple blood draw. A healthcare professional will insert a small needle into a vein in your arm to collect a blood sample. The procedure only takes a few minutes and is generally well-tolerated. You may experience minor bruising or soreness at the puncture site, but serious complications are rare. In most cases, you do not need to fast before the test, though your doctor may provide specific instructions based on your situation.
Understanding your results
Normal ALP levels vary depending on age, sex, and the laboratory that performs the test. Generally, adult normal ranges fall between 20 to 140 units per liter (U/L), though this can differ. Your healthcare provider will interpret your results in the context of your overall health, symptoms, and other test results. It is important to remember that a single test result alone cannot diagnose a condition—further testing may be needed to determine the cause of any abnormal levels.
Reference range
44-147 U/Lnot specified
No fasting or special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated ALP levels (hyperphosphatasemia) are more common than low levels and can indicate various conditions. Liver-related causes include hepatitis (viral or alcoholic), cirrhosis, bile duct obstruction, gallstones, or liver tumors. Bone-related causes encompass Paget's disease, bone metastases, osteomalacia, rickets, or recent bone fractures. Other causes may include heart failure, hyperthyroidism, certain infections, or the use of medications such as statins, antibiotics, or anti-seizure drugs. In children and adolescents, mildly elevated ALP is normal due to bone growth.
Low ALP levels (hypophosphatasemia) are less common but can result from malnutrition, magnesium deficiency, hypothyroidism, Wilson's disease, or certain genetic disorders. In rare cases, low ALP may be associated with bone mineralization problems. Your doctor will investigate the underlying cause if your ALP levels are abnormally low.
Frequently asked questions
Do I need to fast before the ALP test?
Can medications affect my ALP results?
What happens if my ALP is elevated?
Is the ALP test safe during pregnancy?
How often should I have my ALP tested?
Sources
- 1
- 2
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- 4
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