Alkaline Phosphatase Isoenzyme Panel
A blood test that measures the different forms, called isoenzymes, of the alkaline phosphatase enzyme in your bloodstream. This panel helps your doctor identify whether elevated enzyme levels are coming from your liver, bones, intestines, or kidneys, which guides further evaluation and treatment decisions.
{"This test measures specific forms of alkaline phosphatase to determine if elevation comes from liver, bone, or other tissues","Elevated levels may indicate liver disease, bone disorders, or other conditions","The test requires a simple blood draw, usually after fasting","Results help your doctor diagnose the cause of symptoms like abdominal pain or bone pain"}
Key facts at a glance
- LOINC
- 24332-9
- Short code
- ALP ISO
- Synonyms
- ALP Iso Pnl SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- not specified
- Ref low
- 44
- Ref high
- 147
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Electrophoresis/Capillary electrophoresis/Immunoassay
- CPT
- 84080
- SNOMED
- 31317008
- Specimen volume
- 2-5 mL
- Stability
- Room temperature: 24-48 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C): 30 days
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
What is this test?
The alkaline phosphatase isoenzyme panel is a blood test that measures different forms (isoenzymes) of the alkaline phosphatase (ALP) enzyme. While a standard ALP test shows the total amount of this enzyme in your blood, the isoenzyme panel identifies which specific tissue is producing the enzyme—helping doctors pinpoint the exact source of any abnormality.
Where does alkaline phosphatase come from?
Alkaline phosphatase is an enzyme found in many tissues throughout your body. The main sources include: the liver (especially in cells lining bile ducts), bones (in osteoblast cells that build bone), the intestines, and kidneys. Each tissue produces a slightly different form of the enzyme, which can be distinguished in the laboratory.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The sample is then sent to a laboratory where special techniques are used to separate and measure the different isoenzyme forms. You may be asked to fast (not eat) for 8-12 hours before the test, as food can affect some isoenzyme results.
What do the results mean?
The results will show which isoenzyme is elevated: Liver ALP indicates liver disease, hepatitis, bile duct obstruction, or gallbladder problems. Bone ALP suggests increased bone turnover from conditions like Paget's disease, osteomalacia, bone healing after fractures, or certain cancers that affect bone. Intestinal ALP may be elevated in intestinal diseases or after eating, especially in people with blood type O or B.
Reference range
Laboratory/method-dependent (total ALP typically 40-129 U/L adults; isoenzyme fractions as U/L or % of total)not specified
Overnight fasting (8-12 h) preferred to avoid postprandial intestinal ALP elevation
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The alkaline phosphatase isoenzyme panel is particularly valuable when total ALP is elevated but the cause is unclear. It helps distinguish between liver and bone disease, which is essential because these conditions require very different treatments. For example, elevated bone ALP in an older adult may suggest Paget's disease, while elevated liver ALP with other abnormal liver tests may indicate hepatitis or bile duct blockage. This test is also used to monitor treatment response in conditions like bone diseases or to track recovery after liver surgery.
Frequently asked questions
Do I need to prepare for this test?
Is the test painful?
What happens if my results are abnormal?
Can children have this test?
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