Dr Henry WeiGastroenterology & Endoscopy
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Faecal calprotectin: interpreting results in primary care

Use calprotectin to assess possible intestinal inflammation or monitor established IBD. Interpret the value and trend alongside symptoms, infection and medicines.

On this page

Author: Dr Henry Wei. Sources checked 16 October 2026.

In practice

Interpret the trend alongside symptoms

I review the actual value, symptoms, infection risk and medicines before repeating or referring. In established IBD, trends help assess inflammation alongside the patient’s symptoms and specialist plan.

Guidance behind this advice

1. Decide whether inflammation is the question

Consider calprotectin for persistent lower-bowel symptoms, especially diarrhoea, when IBD is possible. Check duration, nocturnal symptoms, bleeding, weight, family history and medicines.

Significant bleeding, iron deficiency anaemia, weight loss, a mass or systemic illness needs assessment independently of the result.

2. Interpret the value in context

IBD, infection, NSAID injury, diverticular inflammation and other disease can raise calprotectin. PPIs may cause modest elevations. Review the history and medicine indications.

Example adult triage bands: BSG IBS guidance, µg/g
ValueSuggested action
Below 100Active inflammation is less likely. Treat a supported diagnosis and agree review.
100–249Review infection and medicines. In a stable patient, repeat after temporary causes resolve.
250 or aboveArrange urgent assessment for possible IBD, with urgency also determined by clinical severity.

3. Act on persistent or changing symptoms

These triage bands guide assessment rather than diagnose IBD. Persistent elevation, a rising trend or a strongly suggestive presentation warrants gastroenterology assessment.

After a lower result, reassess ongoing symptoms for coeliac disease, microscopic colitis, bile acid diarrhoea or other causes. Suspected small-bowel Crohn’s disease may need specialist-selected imaging or capsule.

4. Use trends in established IBD

Review calprotectin with symptoms, CRP, disease location and previous endoscopy or imaging. Symptoms may persist without active inflammation, and inflammation may persist when symptoms are mild.

Check infection, medicines and previous results before escalating treatment. Discuss unexpected changes with the IBD team and follow the agreed monitoring plan.

Clinical pearls

  • Microscopic colitis may have a normal calprotectin and still require colon biopsies.
  • Calprotectin can rise with colorectal cancer, but it is not a cancer screening or exclusion test.
  • µg/g and mg/kg are numerically equivalent units.
Diagrams for patient discussions
Explore the explanation

A useful marker, interpreted with your symptoms

Choose a view
Explanatory diagram
Where faecal calprotectin comes fromSimplified side view of bowel tissue. White circles with lobed centres represent neutrophils, a type of inflammatory white blood cell. A migration arrow points from tissue towards the bowel lumen, with dots representing calprotectin released into bowel contents. A stool container represents laboratory sampling. This is not a quantitative model, histology slide or complete immune pathway. Tissue and sample are separate scales. No diagnostic threshold is shown.A signal of inflammation in a stool sample Calprotectin comes largely from inflammatory white blood cells. Inside the bowelTissue below the surface Calprotectin Stoolsample The result cannot identify the cause of inflammation by itself.

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.

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?

Review symptoms, the calprotectin trend, infection and medicines. Persistent elevation or concerning symptoms may need gastroenterology assessment; selected intermediate results can be repeated after temporary causes have resolved.

Information to share with your patient

Related clinician articles

References

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