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What faecal calprotectin measures
No faecal calprotectin level diagnoses cancer. A result above 50 μg/g flags gut inflammation, usually from inflammatory bowel disease or infection, and a colonoscopy decides whether cancer is the cause.
Faecal calprotectin measures a calcium-binding protein that neutrophils (infection-fighting white blood cells) release when they encounter inflammation in your intestinal tract. Think of neutrophils as your body's emergency responders. When they detect trouble in your gut, they flood the area and release calprotectin as part of their inflammatory arsenal.
In cancer, particularly colorectal cancer, inflammation is a hallmark of tumor development. Your immune system recognizes something isn't right and sends neutrophils to investigate. These cells release calprotectin, which ends up in your stool at concentrations far higher than normal.
This marker differs from blood-based cancer markers because it directly reflects what's happening at the intestinal tissue level. While blood tests might miss early inflammatory changes, faecal calprotectin captures the local immune response where problems actually develop.
The test specifically measures calprotectin concentration in micrograms per gram of stool (μg/g). This quantitative approach allows precise tracking of inflammation intensity over time, making it valuable for both initial detection and monitoring treatment response.
Normal versus optimal calprotectin levels
Reference ranges vary between laboratories, and "normal" and "optimal" aren't identical when evaluating cancer risk.
| Result | Usual meaning | Typical next step |
|---|---|---|
| Under 50 μg/g | Normal for adults; under 25 μg/g is optimal, with minimal intestinal inflammation; 25-50 μg/g is a gray zone | None below 25 μg/g; monitor a 25-50 μg/g result over time |
| 50-250 μg/g | A gray zone, and some labs end it at 150 μg/g; somewhat high levels are linked to infection, NSAIDs, celiac disease, treated IBD, or colorectal cancer | Review symptoms and medications with your care team, and retest within about a month before colonoscopy |
| Over 250 μg/g | Marked intestinal inflammation, often IBD or bacterial food poisoning; colorectal cancer can also exceed 50 μg/g by a wide margin | Colonoscopy or other endoscopy, especially with ongoing symptoms |
Individual baseline matters more than population averages. Your personal trend reveals more than any single measurement. Someone consistently at 15 μg/g who jumps to 45 μg/g shows a concerning pattern, even though 45 μg/g falls within "normal" range.
Age influences interpretation. Older adults often show slightly higher baseline levels due to increased intestinal permeability and chronic low-grade inflammation. Your care team considers your age, symptoms, and health history when interpreting results rather than relying solely on reference ranges.
What a high calprotectin result can mean
Elevated faecal calprotectin levels are significantly higher in colorectal cancer patients compared to controls, often exceeding standard 50 μg/g cutoffs by a wide margin. These high concentrations reflect intense local inflammation around tumor sites.
Research indicates colorectal cancer drives elevation through multiple mechanisms. Tumor cells disrupt normal tissue architecture, triggering immune responses. Cancer-associated bacteria may colonize tumor areas, intensifying inflammation. The tumor itself releases inflammatory signals that recruit neutrophils to the area.
High levels don't automatically mean cancer. Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, commonly produces even higher calprotectin levels than many cancers. Bacterial infections, medication-induced colitis, and severe irritable bowel syndrome can also elevate levels significantly.
Context matters enormously. High calprotectin alongside symptoms like blood in stool, unexplained weight loss, or persistent abdominal pain raises cancer suspicion more than elevated levels alone. Your care team considers symptom patterns, family history, and other biomarkers when determining next steps after high results. Discuss with your care team about the most appropriate follow-up based on your individual situation.
What a low calprotectin result can mean
A low result helps rule out inflammatory bowel disease and may reduce the likelihood of colorectal cancer, but it doesn't eliminate cancer risk entirely.
Early-stage colorectal cancers, particularly small polyps or tumors in early development, might not trigger enough inflammation to significantly elevate calprotectin. Some cancer types may produce less inflammatory response than others, potentially maintaining normal calprotectin levels longer.
Location affects results. Cancers in the upper digestive tract (stomach, small intestine) may not influence faecal calprotectin as dramatically as colorectal cancers. The protein degrades as it travels through the digestive system, so distant inflammation produces less measurable impact.
Consistently low levels provide reassurance about inflammatory conditions but shouldn't replace standard cancer screening. Calprotectin measures inflammation, while the faecal immunochemical test (FIT) uses antibodies to detect blood in stool, so a normal calprotectin result says nothing about hidden bleeding. Colonoscopy remains the gold standard for colorectal cancer detection because it can help identify pre-cancerous polyps and early-stage tumors that haven't yet triggered significant inflammation. Low calprotectin supports overall intestinal health but doesn't substitute for comprehensive screening protocols.
How faecal calprotectin is tested
Faecal calprotectin testing requires a stool sample that you collect at home using a provided container. No dietary restrictions or fasting are necessary, making this test more convenient than many other diagnostic procedures.
Sample collection matters for accuracy. You'll need approximately 5-10 grams of stool (about the size of a walnut) collected in a sterile container. The sample should reach the laboratory within 24-48 hours of collection, though some test kits include preservatives extending this window to several days.
Avoid certain medications before testing if possible. Non-steroidal anti-inflammatory drugs, proton pump inhibitors, and antibiotics can influence results. Your care team will advise whether to discontinue medications temporarily or proceed with testing while noting potential interference.
Testing frequency depends on clinical context. Initial screening might involve single measurement, while monitoring inflammatory conditions or treatment response requires serial testing every 3-6 months. Results typically return within 2-5 business days, providing relatively rapid insight into intestinal inflammation status.
What can change calprotectin levels
Medications significantly impact faecal calprotectin levels. NSAIDs like ibuprofen and naproxen can increase levels by causing intestinal irritation. Proton pump inhibitors may alter gut bacteria composition, potentially affecting calprotectin production. Antibiotics dramatically shift intestinal microbiome balance, often temporarily elevating levels.
Dietary factors influence results through inflammatory pathways. High-processed food diets are associated with increased intestinal permeability and may elevate baseline levels. Alcohol consumption can trigger intestinal inflammation, temporarily raising calprotectin. Fiber intake affects gut bacteria composition, indirectly influencing inflammatory responses.
Infections create temporary spikes. Bacterial gastroenteritis, parasitic infections, and viral illnesses can dramatically increase calprotectin levels for weeks following symptom resolution. Recent illness history helps interpret unexpected elevations.
Stress and exercise affect results through multiple mechanisms. Chronic stress increases systemic inflammation, potentially elevating baseline calprotectin. Intense exercise temporarily increases intestinal permeability, though regular moderate activity typically reduces inflammatory markers long-term. Age-related changes in intestinal barrier function gradually increase baseline levels over decades.
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Connecting faecal calprotectin to related biomarkers
Normal blood tests alongside a high calprotectin point to inflammation localized to the intestine, which is what normal C-reactive protein (CRP) with high calprotectin indicates. Elevated CRP alongside high calprotectin suggests a widespread inflammatory response, and erythrocyte sedimentation rate (ESR) adds the same systemic context.
Complete blood count (CBC) reveals additional inflammatory patterns. Elevated white blood cell count, particularly neutrophils, supports inflammatory interpretation of high calprotectin. Anemia might indicate chronic bleeding associated with intestinal inflammation or malignancy.
Carcinoembryonic antigen (CEA) serves as a complementary cancer marker. While CEA isn't specific for colorectal cancer, combined elevation of CEA and calprotectin may strengthen suspicion for malignancy requiring urgent investigation.
Lactoferrin, another neutrophil-derived protein found in stool, correlates strongly with calprotectin levels. Some laboratories offer both markers, providing confirmatory evidence of neutrophil activity in the intestinal tract. This combination helps differentiate true inflammation from technical measurement issues.
Understanding your faecal calprotectin results
Faecal calprotectin can reveal intestinal inflammation before symptoms become severe, and because the test is non-invasive, people with a family history of colorectal cancer, inflammatory bowel disease, or previous polyps may benefit from monitoring between colonoscopies. Rising levels prompt earlier investigation, and trending results help track IBD treatment or early signs of recurrence. Results mean more alongside blood markers: Superpower's Baseline Blood Panel includes hs-CRP, which shows whether inflammation is systemic or confined to the gut. Work with your care team to set the right monitoring strategy.
Frequently Asked Questions
References
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- Sandberg-Janzon A, Karling P (2025). Prescription of NSAIDs and proton pump inhibitors are associated with increased faecal calprotectin levels in patients with functional bowel disorder: an observational study. *Scandinavian journal of gastroenterology*, *60*(7), 635-642. https://doi.org/10.1080/00365521.2025.2512368
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- Centers for Disease Control and Prevention. (2026). *Screening for colorectal cancer*. https://www.cdc.gov/colorectal-cancer/screening/index.html
- Kapel N, Ouni H, Benahmed NA, Barbot-Trystram L (2023). Fecal Calprotectin for the Diagnosis and Management of Inflammatory Bowel Diseases. *Clinical and translational gastroenterology*, *14*(9), e00617. https://doi.org/10.14309/ctg.0000000000000617
- MedlinePlus. (n.d.). *Calprotectin stool test*. https://medlineplus.gov/lab-tests/calprotectin-stool-test/
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