Intestinal Alkaline Phosphatase (IAP) Test
This blood test checks for intestinal alkaline phosphatase (IAP), an enzyme produced mainly by your intestines that helps your body absorb nutrients and protects the lining of your digestive tract from harmful bacteria and toxins.
{"Intestinal alkaline phosphatase is an enzyme primarily made in the small intestine","It helps digest fats and protects the intestinal lining from bacteria and toxins","This test can help diagnose digestive disorders or intestinal damage","Abnormal levels may indicate conditions like celiac disease, Crohn's disease, or intestinal infections","The test is performed on a blood sample taken from a vein in your arm"}
Key facts at a glance
- LOINC
- 40794-0
- Short code
- ALP-I
- Synonyms
- ALP Intest SerPl Ql
- Category
- chemistry
- Sample
- serum
- Container
- Serum separator tube (SST) or plain red top tube
- Units
- not specified
- Ref low
- 0
- Ref high
- 20
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 18 years
- Method
- Electrophoresis or immunoassay for isoenzyme differentiation
- CPT
- 84075
- SNOMED
- 271509004
- Specimen volume
- 1-2 mL serum minimum
- Stability
- Serum stable at 2-8°C for up to 7 days; frozen at -20°C for longer storage; avoid repeated freeze-thaw cycles
- Hemolysis max
- 50
- Lipemia max
- 300
- Icterus max
- 20
- TAT
- 24–72 hours
- Order
- routine
What is this test?
The intestinal alkaline phosphatase (IAP) test is a blood test that detects the presence and measures the level of a specific type of alkaline phosphatase enzyme that comes from your intestines. Alkaline phosphatase (ALP) is found in various tissues throughout the body, but this test specifically looks at the intestinal variant (IAP).
Why is it important?
Intestinal alkaline phosphatase plays several important roles in your digestive health: It helps break down fats in the food you eat, it protects the intestinal lining from harmful bacteria and bacterial toxins, and it helps maintain a healthy balance of gut bacteria. When the intestines are damaged or inflamed, IAP levels in the blood may change, making this test useful for evaluating intestinal health.
How is the test performed?
A healthcare professional will draw a small blood sample from a vein in your arm. The blood is then sent to a laboratory where it is analyzed to detect the presence of intestinal alkaline phosphatase. You do not need to fast before this test unless your doctor instructs otherwise.
What do the results mean?
Results are typically reported as either 'present' or 'not detected' (qualitative result), or may show a specific level (quantitative result). Your doctor will interpret these results along with your symptoms and other test findings to make a diagnosis.
Reference range
Negativenot specified
Fasting preferred; avoid recent fatty meals which can increase intestinal ALP
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated intestinal alkaline phosphatase levels in blood may indicate: intestinal inflammation or damage (such as in celiac disease, Crohn's disease, or ulcerative colitis), intestinal infections, damage to the intestinal lining from certain medications or toxins, or malabsorption disorders. Low or absent IAP levels are less common but may be associated with certain genetic conditions or severe intestinal damage.
This test is often used alongside other alkaline phosphatase tests (like liver ALP) to determine the source of elevated ALP levels. Since IAP is specific to the intestines, its presence in blood helps doctors pinpoint whether digestive issues are related to intestinal problems.
Frequently asked questions
Do I need to fast before this test?
Is this test painful?
How long does it take to get results?
What happens if my results are abnormal?
Can medications affect my test results?
Sources
- 1
- 2
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