What Can Falsely Raise Calprotectin? Understanding High Levels

Calprotectin is a stool marker that signals neutrophil-driven inflammation in the gut, widely used to differentiate inflammatory bowel disease (IBD) from non-inflammatory conditions like IBS. However, calprotectin can rise for reasons other than chronic disease, which can complicate diagnosis. This guide explains what calprotectin is, what a high result means, the specific causes that can falsely elevate it, and outlines practical steps for interpreting your test and determining appropriate next steps.

What Does It Mean If Calprotectin Is High?

A high fecal calprotectin level primarily indicates inflammation in the digestive tract, often prompting investigation for conditions like Crohn's disease or ulcerative colitis. However, it's not a standalone diagnosis. The result must be interpreted in the context of your symptoms, medical history, and other tests. Importantly, high levels can also be caused by non-chronic issues like infections or medication use, which is why understanding the full range of possibilities is crucial.

How clinicians interpret levels: Results are typically categorized. Values below 50 μg/g are often considered normal, while 50-150/200 μg/g may be borderline. Results above 150-200 μg/g are generally elevated and suggest inflammation, with levels over 500-600 μg/g being markedly elevated and more strongly associated with active IBD. The key takeaway is that a high calprotectin is a signal for further investigation, not a final verdict.

What Cancers Cause High Calprotectin?

Elevated calprotectin can be associated with colorectal cancer and some advanced adenomas (pre-cancerous polyps). The inflammation caused by these growths can lead to an increase in neutrophils and the calprotectin they release. However, it is critical to understand that calprotectin is not a cancer screening test. An elevated level is far more likely to be caused by much more common conditions like IBD, infections, or diverticulitis. A persistently high result warrants a thorough medical evaluation, which may include a colonoscopy, to determine the underlying cause.

Can Food Cause High Calprotectin?

While food does not directly cause a massive spike in calprotectin like an IBD flare or infection can, dietary factors can play a role. Short-term dietary changes, food intolerances (like to high-FODMAP foods), or heavy alcohol use can irritate the gut lining and contribute to low-grade inflammation or dysbiosis in sensitive individuals, potentially nudging calprotectin into a borderline range. The timing of the test also matters; a sample taken soon after a significant dietary indiscretion might show a transient effect. For the most accurate baseline, it's best to maintain your usual diet before testing unless otherwise instructed by your doctor.

How to Manage and Treat High Calprotectin in Stool

"Treating" high calprotectin involves addressing its underlying cause, not the number itself. The management plan depends entirely on the diagnosis. If IBD is confirmed, treatment may include anti-inflammatory medications. If an infection is the cause, antibiotics or supportive care may be needed. For elevations linked to medications like NSAIDs, a clinician may advise discontinuing or switching the drug. A common and important first step for a borderline or unexpected high result is simply to repeat the test after 2-6 weeks, especially if a transient cause like an infection is suspected, to see if the level normalizes.

Core Explanation of Calprotectin and Its Diagnostic Role

What is calprotectin? Calprotectin is a protein complex (S100A8/S100A9) abundant in neutrophils, a type of white blood cell. When the intestinal lining becomes inflamed, neutrophils migrate into the gut lumen and release calprotectin. Because calprotectin remains stable in stool for several days, it serves as a practical, noninvasive marker of intestinal inflammation.

How is calprotectin used? Clinicians commonly use fecal calprotectin to help distinguish inflammatory bowel disease (IBD) from functional gastrointestinal disorders such as irritable bowel syndrome (IBS). Lower values often suggest a non-inflammatory condition; moderate to markedly elevated values increase the likelihood of inflammation. While cut-offs vary by lab and clinical context, many use ranges such as:

• Low/normal: typically below 50 μg/g (adult reference ranges vary)
• Borderline/indeterminate: approximately 50–150/200 μg/g
• Elevated: above 150–200 μg/g
• Markedly elevated: above 500–600 μg/g (more strongly suggests active inflammatory disease)

Conditions linked to elevated calprotectin: Fecal calprotectin can rise in IBD (Crohn’s disease, ulcerative colitis), infectious gastroenteritis, diverticulitis, microscopic colitis, celiac disease (especially if untreated), colorectal neoplasia, ischemic colitis, and after significant mucosal injury. It may also increase transiently after gastrointestinal procedures that disturb the mucosa.

Specific Causes of Falsely Elevated Calprotectin

1) Infections and Post-Infectious States

Acute bacterial gastroenteritis (e.g., Campylobacter, Salmonella, Shigella), Clostridioides difficile, and some parasitic infections (e.g., Giardia) commonly raise calprotectin. Viral infections can elevate it to a lesser degree. Importantly, calprotectin may remain elevated for several weeks after symptoms improve due to ongoing mucosal recovery.

2) Medication Effects

• NSAIDs and aspirin: These drugs can irritate the gastrointestinal lining and increase intestinal permeability, resulting in elevated calprotectin in some users.
• Proton pump inhibitors (PPIs): Some studies—particularly in children—have reported modestly higher fecal calprotectin among PPI users.
• Other agents: Certain chemotherapeutics, mycophenolate, and drugs linked to microscopic colitis can be associated with increased calprotectin.

3) Recent Gastrointestinal Procedures or Trauma

Endoscopy with mucosal biopsies, polypectomy, bowel preparation, and surgical interventions can temporarily raise calprotectin. If your test was collected shortly after a procedure, a repeat after healing (1–4 weeks) can provide a cleaner baseline.

4) Age and Baseline Physiology

Infants and toddlers often show higher normal fecal calprotectin levels due to immune maturation. Older adults may have slightly higher baselines influenced by comorbidities and polypharmacy. Age-appropriate reference ranges are essential.

5) Strenuous Endurance Exercise

Prolonged, intense exercise can temporarily increase intestinal permeability and promote mild mucosal stress, sometimes raising calprotectin. Values typically normalize with rest.

6) Non-IBD Inflammatory Conditions

Microscopic colitis, diverticulitis, ischemic colitis, and celiac disease can elevate calprotectin in ways that mimic IBD signals.

7) Bleeding and Sample Contamination

Heavy bleeding or contamination with menstrual blood may affect results. Most stool collection instructions recommend avoiding sampling during active menstruation.

The Role of the Gut Microbiome in Calprotectin Levels

The gut microbiome supports digestion, immune function, and barrier integrity. When imbalances occur (dysbiosis), it can lead to low-grade inflammation. This can, in some people, cause a modest rise in calprotectin even without overt IBD. Microbial dysbiosis is not a diagnosis but a state that can contribute to symptom sensitivity and borderline inflammation signals.

Practical Steps Before and After a Calprotectin Test

• Timing: Avoid sampling immediately after invasive procedures, acute gastroenteritis, or endurance events.
• Medications: Discuss NSAIDs and other potentially irritating drugs with your clinician before testing.
• Collection: Follow kit instructions carefully; avoid collecting during active menstruation.
• Repeat if needed: If results are borderline or unexpected, a repeat test after removing confounders often clarifies the trend.

FAQ: Common Questions About Calprotectin

What does it mean if calprotectin is high?

A high calprotectin level indicates inflammation in the intestines. While it can be a sign of IBD, it's also commonly elevated by infections, medications like NSAIDs, and other non-chronic conditions. It is a signal for further medical investigation, not a final diagnosis.

What cancers cause high calprotectin?

Colorectal cancer and some advanced polyps can cause inflammation that elevates calprotectin. However, this is a less common cause. An elevated result is far more likely to be due to IBD or other inflammatory conditions and requires proper medical evaluation to determine the cause.

Can food cause high calprotectin?

Food alone is unlikely to cause a major elevation. However, dietary intolerances or heavy alcohol use can contribute to gut irritation and low-grade inflammation in sensitive individuals, potentially leading to a borderline result. For an accurate baseline, maintain your normal diet before testing.

How to treat high calprotectin in stool?

Treatment focuses on the underlying cause. This could mean managing IBD with medication, treating an infection, or adjusting medications like NSAIDs. A common first step for a borderline result is to repeat the test after a few weeks to see if the elevation persists.

Does a normal calprotectin rule out IBD?

A low calprotectin makes active IBD, especially in the colon, less likely but does not completely rule it out. Clinical evaluation is still important if symptoms and suspicion persist.

How long after an infection should I retest calprotectin?

Wait 2-6 weeks after symptoms have resolved to retest, as levels can remain elevated during mucosal healing.

Key Takeaways

• Calprotectin measures gut inflammation but is not disease-specific.
• False or transient elevations are common with infections, NSAIDs, and recent procedures.
• A high result requires clinical context; it can signal IBD but also many other conditions.
• Diet and microbiome imbalances can contribute to borderline elevations.
• Repeat testing is often key to interpreting borderline or unexpected results.
• Persistently high values with symptoms warrant a thorough medical evaluation.

If you have unexplained gut symptoms or a borderline calprotectin result, understanding your gut microbiome can provide additional context. An at-home microbiome test can offer educational insights into your gut ecology to discuss with your healthcare provider.