Cramping, bloating and a change in bowel habit can feel much the same whether the cause is irritable bowel syndrome (IBS), an infection or inflammation. The symptoms alone do not always tell those possibilities apart. That uncertainty is why faecal calprotectin is often an early, practical question: is there measurable inflammation in the bowel?
IBS is a functional bowel condition. It can cause significant symptoms, but it does not usually inflame or damage the bowel lining. Inflammatory bowel disease (IBD), including Crohn’s disease and ulcerative colitis, involves inflammation. Calprotectin gives you and your clinician evidence that can help decide whether inflammatory causes need further investigation.
It is not a stand-alone answer. A raised result does not name the cause, and a result within the laboratory range cannot explain every gut symptom. Your age, medicines, recent infections, symptom pattern and any warning signs all affect what should happen next.
What this test measures
The test measures the concentration of calprotectin in a small stool sample. Calprotectin is abundant in neutrophils, a type of white blood cell. When neutrophils move into the intestinal lining during inflammation, more calprotectin passes into the stool. It remains relatively stable there, which makes stool a useful sample for assessing bowel inflammation.
A low result makes active inflammation less likely in the right clinical setting. A higher result indicates that inflammation may be present, but does not tell you whether it comes from IBD, a gastrointestinal infection, use of certain medicines or another bowel condition. This is why the marker is described as sensitive to inflammation rather than specific to one illness.
Calprotectin is different from a blood inflammatory marker such as C-reactive protein. It reflects activity in the gut more directly. It is also different from a stool culture or PCR panel, which looks for particular bacteria, parasites or viruses rather than measuring the bowel’s inflammatory response.
When testing may be useful
Testing may be useful when you have persistent diarrhoea, abdominal discomfort, bloating or a changed bowel habit and a clinician is considering IBS alongside an inflammatory cause. NICE supports faecal calprotectin testing in appropriate adults with recent lower gastrointestinal symptoms when specialist assessment for cancer is not being considered.
Timing matters. A recent stomach infection can temporarily raise calprotectin. Non-steroidal anti-inflammatory medicines, such as ibuprofen or naproxen, can also affect results in some people. Do not stop prescribed medicine on your own; record what you take and discuss timing with a clinician or the testing service.
Do not wait for a home result if you have blood in your stool, unexplained weight loss, a persistent fever, severe or worsening pain, signs of dehydration, or symptoms that wake you repeatedly at night. New bowel symptoms in an older adult, a strong family history or other concerning features also deserve direct clinical assessment.
What your results can mean
Use the reference information supplied by the reporting laboratory, because methods and action ranges can differ. Results are commonly grouped into a range where active inflammation is less likely, an intermediate range that may need repeating, and a higher range where clinical review or further investigation is more likely to be appropriate.
An intermediate value is not a verdict. Your clinician may ask about infection, medicines and how long symptoms have been present, then repeat the measurement after an interval. A changing result can sometimes be more useful than treating one number in isolation.
A raised result may lead to further stool or blood tests and, when appropriate, referral to gastroenterology. Further assessment can include imaging or endoscopy, but calprotectin itself does not determine which investigation you need. A low result may shift the conversation towards IBS and symptom management, while still leaving room to investigate other causes if symptoms continue.
What to do next
Before collecting your sample, follow the kit instructions closely and note recent diarrhoea, travel, medicines and supplements. Avoid contaminating the sample with toilet water or urine. Return it in the packaging provided and check whether the laboratory has any time or storage requirements.
When the report arrives, read the numerical result, its units, the laboratory range and the clinical comment together. Share the report with your GP if the result is raised, your symptoms are persistent or you are unsure how the number fits your situation. Keep a short symptom record, including stool frequency, visible blood, pain, weight change and foods or medicines that appear relevant.
Calprotectin is most useful as a direction-finding marker: it helps decide whether inflammation needs attention. It should support, not replace, a fuller clinical conversation. If your symptoms change or warning signs appear, seek medical advice even if an earlier result was within range.
See the Calprotectin Test, read when ongoing gut symptoms after travel may need a parasite test, or explore digestive health tests.
References
- NICE: Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel
- North West London Pathology: Calprotectin (faecal)
- NHS Scotland: Calprotectin
Sources: NICE: Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel; North West London Pathology: Calprotectin (faecal); NHS Scotland: Calprotectin — see all references