Alkaline Phosphatase Isoenzymes Test
This blood test measures the different forms of the alkaline phosphatase (ALP) enzyme in your blood, helping your doctor determine whether elevated ALP levels are coming from your liver or your bones.
{"Measures different forms (isoenzymes) of alkaline phosphatase in blood","Helps determine if high ALP comes from liver or bone","Uses levamisole to inhibit specific isoenzyme types","Requires a simple blood draw","Useful in diagnosing liver disease or bone disorders"}
Key facts at a glance
- LOINC
- 33063-9
- Short code
- ALP iso
- Synonyms
- ALP Isos SerPl Lev Inh-cCnc
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain 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
- ≥ 18 years
- Method
- levamisole-inhibition
- CPT
- 84080
- SNOMED
- 271544001
- Specimen volume
- 1-2 mL serum minimum
- Stability
- Room temperature: 2-3 days; Refrigerated (2-8°C): 5-7 days; Frozen (-20°C): 2-3 months; Avoid repeated freeze-thaw cycles
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 4–48 hours
- Order
- routine
What is this test?
The Alkaline Phosphatase Isoenzymes test measures different forms (isoenzymes) of the alkaline phosphatase (ALP) enzyme in your blood. Alkaline phosphatase is an enzyme found in various tissues throughout your body, particularly in the liver, bones, intestines, and kidneys. This test uses a special chemical called levamisole to inhibit (block) certain types of ALP isoenzymes, allowing doctors to determine which tissue is producing the enzyme.
Why do I need this test?
Your doctor may order this test if a routine alkaline phosphatase blood test shows elevated levels. Since ALP can come from different organs, this test helps determine whether the elevated ALP is due to liver disease, bone disorders, or other conditions. It is particularly useful when the cause of elevated ALP is unclear from other tests alone.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The blood is collected into a tube and sent to a laboratory for analysis. In the lab, technicians use levamisole, which specifically inhibits intestinal alkaline phosphatase, allowing them to measure the remaining ALP activity and determine the source.
How to prepare for the test?
Follow your doctor's instructions regarding fasting, as some isoenzyme levels may be affected by food intake. Inform your doctor about all medications you are taking, as certain drugs can affect ALP levels. Avoid strenuous exercise before the test, as it may temporarily increase ALP levels.
Reference range
Laboratory-specific (typically residual activity after levamisole ~15-60 U/L for bone fraction or % of total ALP; no universal adult range)not specified
No special preparation or fasting required
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated liver ALP isoenzymes may indicate conditions such as hepatitis, cirrhosis, bile duct obstruction, or liver tumors. Elevated bone ALP isoenzymes may suggest bone diseases like Paget's disease, osteoporosis, bone fractures, or conditions with increased bone turnover. This test helps doctors differentiate between liver and bone causes, guiding appropriate treatment and further testing.
Frequently asked questions
What do high alkaline phosphatase isoenzyme levels mean?
Is the test painful?
How long does it take to get results?
Are there any risks associated with this test?
Do I need any follow-up testing?
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