Stool Tests: Fecal Calprotectin

Fecal calprotectin measures a protein released by white blood cells in the gut. High levels in stool point to intestinal inflammation. This simple, noninvasive test helps tell inflammatory bowel disease (IBD) apart from functional problems like irritable bowel syndrome, and it tracks how well treatment is working over time. It can also reduce how often scopes are needed, when used in a monitoring plan.

Key takeaways

• Fecal calprotectin reflects gut inflammation and correlates well with endoscopic activity, especially in ulcerative colitis. (pubmed.ncbi.nlm.nih.gov)

• Typical adult cutoffs: under 50 µg/g is usually normal; 50–150 is a gray zone; above 150 suggests active inflammation in the right context. Lab reference ranges vary. (pubmed.ncbi.nlm.nih.gov)

• In remission, many care teams check fecal calprotectin every 6–12 months; during active symptoms or after a therapy change, every 2–4 months. (gastro.org)

• Medicines like NSAIDs and some proton pump inhibitors, and infections, can raise results even without an IBD flare. Retesting is often needed. (pubmed.ncbi.nlm.nih.gov)

• Home tests can work well for trending values, but very high readings are best confirmed in a lab. Use the same brand over time. (pubmed.ncbi.nlm.nih.gov)

What fecal calprotectin measures

Calprotectin is a protein from neutrophils, a type of white blood cell. When the gut lining is inflamed, neutrophils release calprotectin into the bowel, which then appears in stool. Measuring it in micrograms per gram (µg/g) gives a snapshot of inflammation inside the intestines without a scope. Compared with blood markers like C‑reactive protein, it is more specific to the gut. (bmcgastroenterol.biomedcentral.com)

How the test helps in IBD care

• Distinguishing IBD from IBS: A low fecal calprotectin makes ongoing inflammation much less likely. In adults, pooled data show high accuracy for ruling out IBD when using lower cutoffs, which helps avoid unnecessary colonoscopies. (pubmed.ncbi.nlm.nih.gov)

• Tracking disease activity: Levels rise with mucosal inflammation and fall as inflammation heals. The link is strongest in ulcerative colitis and in Crohn’s disease that involves the colon. Correlation is weaker in isolated small‑bowel Crohn’s, though newer studies suggest useful cutoffs in selected settings. (pubmed.ncbi.nlm.nih.gov)

• Treat‑to‑target: Modern care aims for symptom control plus objective healing. Guidelines include normalization of stool biomarkers as a target and allow biomarker‑first monitoring between scopes. (pubmed.ncbi.nlm.nih.gov)

Interpreting results

Cutoffs vary by laboratory and by clinical context. For many adults with ulcerative colitis in symptomatic remission, a value under 150 µg/g helps rule out active disease and avoid routine endoscopy. (pubmed.ncbi.nlm.nih.gov)

When and how often to test

• In symptomatic remission: Many teams check every 6 to 12 months, often alongside blood work. (pubmed.ncbi.nlm.nih.gov)

• With new or worsening symptoms: Testing every 2 to 4 months can guide adjustments, with endoscopy reserved for unclear or high‑risk situations. (gastro.org)

• After Crohn’s surgery: Serial fecal calprotectin helps screen for recurrence. A cutoff near 150 µg/g is commonly used to trigger further evaluation, though endoscopy remains the standard to confirm recurrence. (pubmed.ncbi.nlm.nih.gov)

What else can raise fecal calprotectin

Fecal calprotectin is not disease‑specific. Results can rise with gastrointestinal infections, diverticulitis, colorectal cancer, celiac disease, and after recent nonsteroidal anti‑inflammatory drug (NSAID) or some proton pump inhibitor (PPI) use. When results are only mildly elevated, clinicians often repeat testing after addressing these factors. (pubmed.ncbi.nlm.nih.gov)

Practical testing tips

• Collection: Use the provided clean container. A small sample is enough.

• Storage and transport: If possible, refrigerate the sample and deliver within 72 hours, or freeze if a delay is expected. Follow kit or lab instructions. Many labs accept refrigerated samples for up to 3 days. (uchicagomedlabs.testcatalog.org)

• Home testing: Several smartphone‑read tests align well with lab methods for values below 500 µg/g. Very high or unexpected results should be confirmed by the laboratory, and it is best to stick with the same brand over time. (pubmed.ncbi.nlm.nih.gov)

• Children: Normal values are higher in infants and fall with age. Pediatric cutoffs differ from adult cutoffs, especially under age 4. (pmc.ncbi.nlm.nih.gov)

Strengths and limits

Fecal calprotectin is a sensitive, gut‑focused indicator that supports faster decisions and fewer scopes. It works best for colonic disease. Isolated small‑bowel Crohn’s may need imaging or capsule endoscopy, even when fecal calprotectin is low. Trends over time, paired with symptoms and occasional endoscopy, offer the clearest picture. (pubmed.ncbi.nlm.nih.gov)

FAQs

Can fecal calprotectin predict a flare

Rising levels can precede symptoms in some people. Many teams act on a clear upward trend, especially when numbers cross 150–250 µg/g, while confirming with endoscopy if decisions are high‑stakes. (journals.lww.com)

What if symptoms are bad but fecal calprotectin is normal

Symptoms do not always match inflammation. Normal results suggest non‑inflammatory causes or irritable bowel patterns. Clinicians may still order imaging or a scope if concern remains high. (gastro.org)

Should NSAIDs or PPIs be avoided before testing

These medicines can raise fecal calprotectin in some people. Many clinicians review necessity and timing, then repeat testing if results are borderline. Decisions should be individualized. (pubmed.ncbi.nlm.nih.gov)

How does fecal calprotectin compare with C‑reactive protein (CRP)

CRP is a blood marker of general inflammation. Fecal calprotectin is more specific to bowel inflammation and often tracks colonic disease more closely, especially in ulcerative colitis. Both are useful together. (pubmed.ncbi.nlm.nih.gov)

How soon do results come back

Many laboratories report within 3 to 5 days, but timing varies by site and shipping. Follow local lab instructions for the most accurate timeline. (uchicagomedlabs.testcatalog.org)