Calprotectin
Also known as: Fecal Calprotectin, Stool Calprotectin
What Does Calprotectin Measure?
Calprotectin is a protein found primarily in neutrophils (a type of white blood cell) that is released into the intestinal tract when inflammation is present in the gut. Fecal calprotectin measures the concentration of this protein in a stool sample, providing a direct indication of intestinal inflammation. Because calprotectin is stable in stool for several days at room temperature, it serves as a reliable and non-invasive marker of gut inflammation.
Why Does Calprotectin Matter?
Fecal calprotectin is a powerful clinical tool used to distinguish between inflammatory bowel diseases (IBD), such as Crohn's disease and ulcerative colitis, and non-inflammatory functional disorders like irritable bowel syndrome (IBS). Elevated levels indicate active intestinal inflammation and can guide decisions about colonoscopy, treatment changes, or medication adjustments. It is also used to monitor disease activity in known IBD patients, predict relapses, and assess whether treatments are working, making it one of the most cost-effective and patient-friendly biomarkers in gastroenterology.
Normal Ranges
Males
Less than 50 µg/g stool (some labs use <200 µg/g as upper threshold)
Females
Less than 50 µg/g stool (some labs use <200 µg/g as upper threshold)
Children
Varies by age; infants may have levels up to 500 µg/g; children under 4 years often have higher baseline levels
Causes of High Levels
- Inflammatory bowel disease (Crohn's disease or ulcerative colitis) — active flares significantly elevate levels
- Infectious gastroenteritis — bacterial, viral, or parasitic gut infections trigger neutrophil infiltration
- Colorectal cancer or polyps — tumors can cause local inflammation and raise calprotectin
- Use of NSAIDs or aspirin — these medications can inflame the gut lining and increase calprotectin
- Celiac disease — active or poorly controlled celiac disease causes intestinal inflammation
- Microscopic colitis — inflammation not visible to the naked eye during colonoscopy but detectable via calprotectin
Causes of Low Levels
- Irritable bowel syndrome (IBS) — a functional disorder without true inflammation, typically shows normal or low calprotectin
- IBD in remission — successful treatment and disease control returns levels to normal range
How to Improve Your Calprotectin
Diet
- Follow an anti-inflammatory diet rich in fruits, vegetables, omega-3 fatty acids (fatty fish, flaxseeds), and whole grains to reduce gut inflammation
- Increase prebiotic fiber intake (garlic, onions, leeks, bananas) to support beneficial gut bacteria and reduce inflammatory signaling
- Reduce consumption of ultra-processed foods, refined sugars, and red/processed meats, which promote gut inflammation
- Consider a Mediterranean diet pattern, which has shown evidence in reducing inflammatory markers including calprotectin in IBD patients
- Eliminate known dietary triggers (e.g., gluten if celiac is confirmed, high-FODMAP foods if contributing to gut symptoms) to reduce mucosal stress
Supplements
- Probiotic strains (Lactobacillus and Bifidobacterium species, 10–50 billion CFU/day) — clinical evidence supports their role in reducing gut inflammation and calprotectin in some IBD patients
- Omega-3 fish oil (2–4 g/day of combined EPA and DHA) — has anti-inflammatory properties and may help reduce intestinal inflammation
- Vitamin D3 (1,000–4,000 IU/day, adjusted to serum levels) — deficiency is common in IBD and linked to increased disease activity; supplementation may help lower calprotectin
Related Biomarkers
Frequently Asked Questions
What is a dangerously high calprotectin level?
While there is no single universally 'dangerous' threshold, levels above 250 µg/g suggest active intestinal inflammation that warrants further investigation, and levels above 500–1,000 µg/g are strongly associated with active IBD flares or significant pathology like colorectal cancer or serious infection. Any significantly elevated result should be reviewed by a gastroenterologist promptly, as it often triggers further diagnostic workup including colonoscopy.
Can calprotectin distinguish IBS from IBD?
Yes, this is one of its most important clinical uses. Patients with IBS typically have calprotectin levels below 50 µg/g, while those with active IBD (Crohn's disease or ulcerative colitis) usually show levels above 200–250 µg/g. A normal calprotectin result in someone with gut symptoms makes IBD much less likely and can help avoid unnecessary invasive procedures like colonoscopy. However, no test is 100% accurate, and clinical context is always important.
Does calprotectin go up with IBS?
Generally, no. IBS is a functional gastrointestinal disorder characterized by gut motility and sensitivity issues without true mucosal inflammation. As a result, fecal calprotectin levels are typically normal (below 50 µg/g) in people with IBS. If calprotectin is elevated in someone with IBS-like symptoms, it suggests an underlying inflammatory cause that needs further evaluation, such as IBD, infection, or microscopic colitis.
How is the fecal calprotectin test performed?
The test involves collecting a small stool sample at home using a kit provided by your doctor or laboratory. You scoop a small amount of stool into a collection vial and return it to the lab within the specified timeframe (usually within 3 days if kept refrigerated). The sample is then analyzed to measure calprotectin concentration in micrograms per gram of stool (µg/g). It is entirely non-invasive, painless, and does not require any bowel preparation or dietary restrictions in most cases.