Quick answer: Faecal calprotectin is a protein released by white blood cells when there is inflammation in the bowel. A normal result makes inflammatory bowel disease (Crohn's disease or ulcerative colitis) much less likely in someone with IBS-type symptoms, which is why doctors use it to decide who needs further investigation. A raised result does not tell you the cause: infections, some medications such as anti-inflammatory painkillers, and other bowel conditions can also push it up. A high calprotectin always needs to be followed up with your doctor.
Calprotectin is one of the stool markers I see most often in people who come to me with digestive symptoms – sometimes requested by their GP or gastroenterologist, sometimes as part of a broader stool panel. It is also one of the most misunderstood. If you are still working out whether your symptoms look more like IBS or SIBO, my article on SIBO vs IBS is a helpful companion to this one.
What is faecal calprotectin?
Calprotectin is a protein found mainly inside neutrophils, a type of white blood cell. When the lining of the bowel is inflamed, neutrophils move into the area and calprotectin ends up in the stool, where it stays stable for several days. That makes it a practical, non-invasive way to estimate whether there is inflammation in the gut.
Why do doctors test calprotectin in people with IBS symptoms?
IBS and inflammatory bowel disease (IBD) can cause similar symptoms: pain, bloating, diarrhoea and urgency. IBS does not cause visible inflammation; IBD does. A meta-analysis found that a normal calprotectin made IBD very unlikely in adults with IBS-type symptoms, helping many people avoid an unnecessary colonoscopy.1 Studies in everyday gastroenterology practice support its use as a screening step.3
In other words, calprotectin is less about finding a label and more about deciding who needs a closer look.
What is a normal calprotectin level?
Cut-offs vary between laboratories, so always check the reference range on your own report. Many labs regard results below about 50 µg/g as normal, results between roughly 50 and 200 µg/g as a grey zone that is often repeated, and higher results as a reason for referral. Practical guidance for doctors recommends interpreting the number alongside age, symptoms and medication, and repeating borderline results rather than reacting to a single value.2
What can raise calprotectin apart from IBD?
- Gut infections – bacterial, viral or parasitic, including after travel.
- Medication – non-steroidal anti-inflammatory drugs (ibuprofen, naproxen, aspirin) and proton pump inhibitors are well-known causes of a raised result.
- Other bowel conditions – such as diverticular inflammation, microscopic colitis, coeliac disease and polyps or bowel cancer.
- Age and sample handling – results can be higher in young children, and a sample left too long before reaching the lab can be less reliable.
This is exactly why a raised result needs medical follow-up rather than guesswork.
When to see your doctor first
- any calprotectin result your lab flags as raised
- blood or mucus in your stool
- diarrhoea lasting more than a few weeks or waking you at night
- unintentional weight loss, fever or night sweats
- anaemia or tiredness that does not lift
- a family history of IBD or bowel cancer together with new symptoms
My calprotectin is normal but I still feel unwell. Now what?
A normal result is reassuring, but it does not mean your symptoms are imaginary or that nothing can be done. Many people with normal inflammatory markers still have bloating, irregular bowels or pain linked to gut-brain signalling, digestion, transit, food choices or bacterial balance. This is where a root-cause, nutritional approach can work alongside your doctor's care. If you feel you have tried everything, you may find IBS: why nothing has worked useful.
Can diet lower calprotectin?
There is no specific food or supplement that should be used to 'bring down' a raised calprotectin before the cause is known – doing so could delay important care. Once your doctor has investigated, a personalised eating plan may support overall gut comfort and resilience alongside any medical plan. Supplements, if considered at all, are optional and individualised.
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Book your free 15-minute call →Frequently asked questions
Does a high calprotectin mean I have Crohn's or colitis?
Not necessarily. It shows inflammation, but infections, anti-inflammatory painkillers and other bowel conditions can also raise it. Your doctor will decide what further tests are needed.
Can stress raise calprotectin?
Stress is not a recognised direct cause of a raised calprotectin. It can certainly worsen gut symptoms, but a high result should not be put down to stress without medical review.
Should I repeat a borderline calprotectin?
Doctors often repeat results in the grey zone after a few weeks, ideally after stopping anti-inflammatory painkillers if that is safe for you. Follow your doctor's guidance.
Is calprotectin part of a home microbiome test?
Some broader functional stool panels include it; many microbiome-only tests do not. If calprotectin is raised on any test, share it with your doctor.
Can nutritional therapy help if calprotectin is normal?
It may support you in exploring factors such as eating habits, digestion, transit and stress that are commonly associated with ongoing symptoms, always alongside your doctor's care.
References
- A meta-analysis of the utility of C-reactive protein, erythrocyte sedimentation rate, fecal calprotectin, and fecal lactoferrin to exclude inflammatory bowel disease in adults with IBS. PubMed: PMID 25732419
- Practical guidance on the use of faecal calprotectin. PubMed: PMID 29588834
- Faecal calprotectin for differentiating between irritable bowel syndrome and inflammatory bowel disease: a useful screen in daily gastroenterology practice. PubMed: PMID 28839790
This article is for educational purposes and is not medical advice. Nutritional therapy does not replace medical care. Always work with your doctor for any persistent or new symptoms and before making changes to your care, medication or supplements.