Decide whether inflammation needs further investigation
I check the actual result alongside your symptoms, medicines, blood tests and any recent bowel infection. A modest rise may settle, while a persistent or substantial rise may lead to colonoscopy or imaging.
For people with established inflammatory bowel disease, symptoms and inflammation do not always change together. Persistent symptoms can have a non-inflammatory cause, so stronger IBD treatment is not always the answer. Conversely, inflammation can remain active when symptoms are mild. I assess both before changing treatment. Serial faecal calprotectin tests can be useful in this context to monitor the trend over time.
A useful marker, interpreted with your symptoms
What is measured?
Calprotectin is a protein linked to inflammatory white blood cells. The laboratory measures it in poo. It is a clue about inflammation, not a diagnosis of Crohn’s disease, ulcerative colitis or cancer.
What is measured?
Calprotectin is a protein linked to inflammatory white blood cells. The laboratory measures it in poo. It is a clue about inflammation, not a diagnosis of Crohn’s disease, ulcerative colitis or cancer.
Why can it rise?
IBD is one possible cause. Infection, some medicines and other bowel conditions can also raise the result. I interpret the number with your symptoms and other tests.
How is a result interpreted?
The laboratory flag and a referral threshold are different. A lower result makes active inflammation less likely in the right setting, while a value above about 250 µg/g makes active IBD more likely. Neither result is diagnostic, and warning symptoms need assessment regardless of the number.
What happens next?
I decide whether to review, repeat a sample or arrange further investigation from the whole assessment. Auckland laboratory acceptance rules and overseas clinical pathways serve different purposes. A test acceptance rule is not an instruction to delay urgent care.
Simplified illustrations, not to scale. These show an example, not your own anatomy or test result.
Read every diagram explanation
What is measured?
Calprotectin is a protein linked to inflammatory white blood cells. The laboratory measures it in poo. It is a clue about inflammation, not a diagnosis of Crohn’s disease, ulcerative colitis or cancer.
Why can it rise?
IBD is one possible cause. Infection, some medicines and other bowel conditions can also raise the result. I interpret the number with your symptoms and other tests.
How is a result interpreted?
The laboratory flag and a referral threshold are different. A lower result makes active inflammation less likely in the right setting, while a value above about 250 µg/g makes active IBD more likely. Neither result is diagnostic, and warning symptoms need assessment regardless of the number.
What happens next?
I decide whether to review, repeat a sample or arrange further investigation from the whole assessment. Auckland laboratory acceptance rules and overseas clinical pathways serve different purposes. A test acceptance rule is not an instruction to delay urgent care.
What does the test measure?
Calprotectin is a protein in certain white blood cells. When the bowel lining is inflamed, more of it can appear in poo. The test measures this inflammation, but cannot tell us its cause on its own.
Results may be reported in micrograms per gram (µg/g) or milligrams per kilogram (mg/kg). These units have the same numerical value.
Why might the test be useful?
If you have ongoing diarrhoea or other symptoms that raise this question, calprotectin can help decide whether inflammatory bowel disease (IBD) needs further investigation. IBD includes Crohn’s disease and ulcerative colitis. IBS is a different condition and does not usually cause the inflammation this test measures.
A reassuring result can support an IBS assessment when the symptom pattern and other tests fit. It does not mean the symptoms are imaginary. The test is also used to monitor established IBD, where the person’s previous results, disease location and treatment provide a different context from a first test.
Does a raised result mean I have IBD?
No. Bowel infection, diverticular inflammation and some medicines can raise calprotectin. Examples include anti-inflammatory painkillers such as ibuprofen and, sometimes, proton pump inhibitors such as omeprazole. Other bowel conditions can also cause a rise. The number does not identify the cause.
I ask about a recent stomach bug, travel, bleeding and medicines, then check whether stool infection testing or another investigation is more appropriate. Do not stop prescribed medicine to improve the number without discussing it with your GP or clinical team.
What happens with a modest or borderline rise?
A result just outside the laboratory range is different from a much larger rise, but there is no single worldwide cut-off that decides everyone’s care. If there are no concerning features, a repeat after an agreed interval may show whether a temporary rise has settled.
If the result stays raised, rises further or does not fit the symptoms, I reconsider the diagnosis and whether endoscopy or imaging would help. A repeat is useful only when we know what decision it will inform. Repeating samples very close together may not help and may not meet local laboratory criteria.
What can a low result miss?
A low result makes significant bowel inflammation less likely in an appropriately assessed person, but it does not exclude every condition.
Calprotectin can be less reliable for Crohn’s disease confined to the small bowel than for inflammation in the colon. Microscopic colitis may not necessarily produce a raised calprotectin result, so it can still need assessment.
Calprotectin can be elevated in some people with colon cancer, but it is not a bowel cancer screening test and cannot diagnose or rule out cancer. It is not a replacement for a recommended colonoscopy. Persistent bleeding, unexplained iron deficiency, weight loss or an examination finding should not be dismissed because the number is low.
How is it different from FIT or an infection test?
These poo tests assess different things. One normal result cannot replace the others or an investigation already recommended.
| Option | What it measures | How it helps |
|---|---|---|
| Calprotectin | An inflammatory marker. | Supports assessment or monitoring of bowel inflammation. |
| FIT | Human blood in poo. | Bowel screening or prioritising investigation of bowel symptoms. |
| Infection tests | Specific bacteria, parasites or other organisms. | Investigates an infection suggested by symptoms or exposures. |
Taking the sample and agreeing the next step
Use the collection kit and instructions from your laboratory, including storage and return requirements. Let the clinician know if you are acutely unwell or the sample may have been contaminated. Different stool tests may need separate containers, so check before collecting several samples.
Bring the actual report and previous values to your appointment. I will explain whether you need a repeat test, another investigation or treatment for a different cause. If I arrange your test, our team will explain how you will receive the result. Please get in touch if it has not arrived when expected.
Do not wait for a stool result if you are getting worse
Persistent rectal bleeding, unexplained weight loss, iron deficiency or diarrhoea that continues or worsens needs clinical review, even with a low result. Severe pain, significant bleeding, repeated vomiting, fever with marked illness or dehydration need urgent assessment.
Call 111 if you collapse or are too unwell to travel safely. Do not wait for a routine appointment or an email reply.
Three things to remember
- Calprotectin indicates inflammation. It does not identify the diagnosis by itself.
- I interpret the result alongside your symptoms, medicines, laboratory comments and previous results.
- Calprotectin can rise in some colon cancers, but it is not a bowel cancer screening test or a replacement for recommended investigation.
Related information
Sources and further reading
English clinical master checked 16 October 2026.
- Awanui Northern and LabPLUS: local calprotectin criteria (December 2025)
- Health NZ Waikato: calprotectin laboratory guide
- BSG: IBS guideline (2021)
- BSG: IBD guideline (2025)
- BSG: investigating chronic diarrhoea (2018)
- NICE: calprotectin diagnostic testing, migrated to HTG320 in December 2025
- NICE: FIT and its distinction from IBD investigation (2023)