Faecal Calprotectin: Testing for Gut Inflammation

If you have ongoing tummy trouble, one of the most useful questions is whether there is genuine inflammation inside the bowel, or whether the gut is simply behaving irritably. A faecal calprotectin test helps answer exactly that. It is a straightforward home stool test that looks for a marker of inflammation, and it can save you a great deal of uncertainty.

What calprotectin is and why it rises

Calprotectin is a protein found inside certain white blood cells. When the lining of the bowel becomes inflamed, these cells gather at the site and release calprotectin, which then passes into the stool. Measuring it therefore gives an indirect but reliable signal of how much inflammation is present in the bowel wall.

Because it is measured in a stool sample rather than blood, it reflects what is happening locally in the gut. A higher level suggests more active inflammation, while a low level suggests the bowel lining is calm.

The IBD-versus-IBS distinction and why it matters

One of the most valuable uses of this test is helping to separate inflammatory bowel disease (IBD) — which includes Crohn's disease and ulcerative colitis — from irritable bowel syndrome (IBS). The symptoms can overlap considerably: both can cause changeable bowel habits, cramping and discomfort. The crucial difference is that IBD involves real inflammation of the bowel, whereas IBS does not.

This distinction matters because the two conditions are managed in very different ways. IBD often needs specialist assessment and medication to control inflammation, while IBS is usually managed through diet, lifestyle and symptom-based approaches. Getting the direction of travel right early helps you and your doctor focus on the right next steps.

What a raised or normal result means

A raised result points towards inflammation, but it does not, on its own, tell you the exact cause. As well as IBD, levels can rise with a gut infection or after taking certain medicines such as NSAIDs (anti-inflammatory painkillers like ibuprofen). This is why the result always needs to be interpreted alongside your symptoms and history rather than in isolation.

A low or normal result is reassuring. It makes inflammatory bowel disease much less likely and can support a diagnosis of IBS, sparing you more invasive investigations. It is not an absolute all-clear, but it is a meaningful piece of the picture.

Using the home kit and getting it interpreted

The test is done with a simple home kit, so there is no need to attend a clinic to provide the sample. That convenience makes it easier to check something that many people find awkward to discuss. Once you have your result, it is important to review it with a clinician who can weigh it against your symptoms, any medicines you take and your overall health.

Remember that calprotectin is a screening and monitoring tool, not a final diagnosis. Where IBD is suspected, the diagnosis is confirmed by a specialist, usually with a colonoscopy and biopsy that allow the bowel lining to be examined directly.

When to see a doctor

Please seek medical advice promptly if you notice blood in your stool, unexplained weight loss, persistent diarrhoea lasting more than a couple of weeks, symptoms that wake you at night, or a fever alongside gut symptoms. A test result is only one part of the picture, and worrying or ongoing symptoms always deserve a proper assessment by a doctor.

Written by Dr Ibrar Ahmed — MBChB MRCP MRCGP PhD PG Dip (Cardiology)
Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic