Alkaline Phosphatase (ALP) Blood Test
A blood test that measures the amount of alkaline phosphatase, an enzyme found in several tissues throughout your body, including the liver and bones.
{"ALP is an enzyme that helps detect liver and bone disorders","Higher than normal levels may indicate liver disease, bone disease, or bile duct obstruction","The test is performed on a blood sample collected from a vein in your arm","Results are often interpreted together with other liver function tests","Certain medications, pregnancy, or growing bones in children can affect ALP levels"}
Key facts at a glance
- LOINC
- 34568-6
- Short code
- ALP
- Synonyms
- ALP Fld Ql
- Category
- chemistry
- Sample
- serum
- Container
- SST (Serum Separator Tube) / Gold top vacutainer, or red top tube
- Units
- not specified
- Ref low
- 44
- Ref high
- 147
- Critical range
- — – 500 not specified
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Colorimetric assay using p-nitrophenyl phosphate (pNPP) substrate at 405 nm wavelength
- CPT
- 84075
- SNOMED
- 271509001
- Specimen volume
- 3.5-5 mL of whole blood, yielding approximately 1-2 mL serum
- Stability
- Room temperature: 2-3 days; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 1 month. Protect from light.
- 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 a protein found in many tissues throughout your body, including your liver, bile ducts, bones, intestines, and kidneys. The test helps doctors evaluate how well these organs are functioning and detect possible diseases.
Why do I need this test?
Your doctor may order an ALP test as part of a routine liver function panel or if you have symptoms such as jaundice (yellowing of skin or eyes), abdominal pain, nausea, or unexplained itching. The test helps determine whether you have liver disease, bone disorders, or conditions affecting your bile ducts.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The sample is then sent to a laboratory for analysis. You typically do not need to fast before this test, but follow any specific instructions your doctor provides.
Understanding your results
Normal ALP levels vary by age, sex, and blood type. High levels may indicate liver problems (such as hepatitis, cirrhosis, or bile duct obstruction), bone disorders (such as Paget's disease or bone cancer), or other conditions. Low levels are less common but can be associated with malnutrition, zinc deficiency, or certain genetic disorders. Your doctor will interpret your results in context with other tests.
Reference range
Negativenot specified
No special preparation required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated ALP is commonly associated with liver diseases such as hepatitis, gallstones, or liver tumors. It can also indicate bone disorders including osteoporosis, bone metastases, or Paget's disease. Since ALP exists in multiple tissue types, doctors often order additional tests (like GGT or bilirubin) to determine whether the source is liver or bone-related.
The test is also used to monitor the effectiveness of treatments for liver or bone diseases, and to check for drug-induced liver injury in patients taking certain medications that may affect liver function.
Frequently asked questions
Do I need to fast before the ALP test?
What can cause false high ALP results?
Is the ALP test dangerous?
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 10, 2026. · Read our editorial policy