Alkaline Phosphatase (ALP) Blood Test
A blood test that measures the level of alkaline phosphatase (ALP), an enzyme found in tissues throughout your body, including the liver, bones, and intestines. This test helps your doctor evaluate how well these organs are working and check for possible conditions affecting them.
{"Alkaline phosphatase is an enzyme important for breaking down proteins in your body","Elevated levels may indicate liver disease, bone disorders, or other conditions","The test is performed on a blood sample taken from a vein in your arm","Normal levels vary by age, gender, and blood type","Certain medications and pregnancy can affect test results"}
Key facts at a glance
- LOINC
- 109532-2
- Short code
- ALP-BF
- Synonyms
- ALP Msmt Fld
- Category
- chemistry
- Sample
- serum
- Container
- Red-top serum tube or sterile container for body fluid collection
- Units
- not specified
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Colorimetric assay using p-nitrophenyl phosphate (pNPP) substrate
- CPT
- 82164
- SNOMED
- 271509003
- Specimen volume
- 1-2 mL of body fluid; minimum 0.5 mL
- Stability
- Room temperature: 7 days; Refrigerated (2-8°C): 14 days; Frozen (-20°C): 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 2–24 hours
- Order
- routine
What is Alkaline Phosphatase?
Alkaline phosphatase (ALP) is an enzyme—a type of protein that helps speed up chemical reactions in your body. It is found in many tissues throughout the body, with the highest concentrations in the liver, bones, intestines, and kidneys. The enzyme plays a crucial role in removing phosphate groups from molecules, which is important for various bodily processes including bone formation and liver function.
Why is This Test Performed?
Your healthcare provider may order an alkaline phosphatase test to: evaluate liver function and detect liver diseases such as hepatitis or cirrhosis; identify bone disorders including Paget's disease, osteomalacia, or bone tumors; diagnose conditions affecting the bile ducts, such as gallstones or cholestasis; monitor the effectiveness of treatment for liver or bone diseases; or investigate the cause of symptoms like jaundice, abdominal pain, or bone pain.
How is the Test Performed?
A healthcare professional will draw a blood sample from a vein in your arm using a small needle. The procedure typically takes only a few minutes. You may feel a brief stinging sensation when the needle is inserted or removed. The blood sample is then sent to a laboratory where the level of alkaline phosphatase is measured. You usually do not need to fast before this test, though your doctor may instruct you to do so based on your specific situation.
Understanding Your Results
Normal alkaline phosphatase levels vary depending on age, sex, and blood type. Generally, the normal range for adults is 20 to 140 units per liter (U/L), though this can vary by laboratory. Children and adolescents typically have higher levels due to bone growth. Elevated ALP may indicate liver disease, bone disorders, gallbladder problems, or other conditions. Low ALP levels are less common but can result from malnutrition, zinc deficiency, or certain genetic disorders. Your doctor will interpret your results in the context of your overall health and other test findings.
Reference range
Adult: 44-147 U/Lnot specified
No special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Alkaline phosphatase testing provides valuable information about liver and bone health. Elevated ALP levels are commonly associated with liver conditions such as hepatitis, cirrhosis, gallstones, or bile duct obstruction. In bone disorders, increased ALP indicates increased bone activity, which occurs in conditions like Paget's disease, bone metastases, osteomalacia, or during fracture healing. The test is often used alongside other liver function tests (such as ALT, AST, and bilirubin) to get a complete picture of liver health. Isolated ALP elevation requires further investigation to determine whether the source is liver or bone, often through additional testing or imaging studies.
Frequently asked questions
Do I need to fast before the alkaline phosphatase test?
Can medications affect my ALP levels?
Why would my doctor order this test along with other tests?
What does a high ALP level mean if I feel healthy?
How long does it take to get 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 16, 2026. · Read our editorial policy