Fecal calprotectin is a stool test that measures a protein released by neutrophils, a type of white blood cell, in the intestinal lining. It helps doctors determine if gut symptoms like diarrhea, abdominal pain, or bloating are due to inflammation—such as inflammatory bowel disease (IBD)—or a non-inflammatory condition like irritable bowel syndrome (IBS). This article explains what calprotectin levels mean, what ranges are considered normal, borderline, or concerning, and what to do if your results are elevated, with practical next steps and the role of gut microbiome testing.

What Is Fecal Calprotectin and Why Is It Tested?

Calprotectin is a calcium- and zinc-binding protein that is abundant in neutrophils. When the gut is inflamed, neutrophils migrate into the intestinal mucosa and release calprotectin, which is then excreted in stool. Measuring this protein provides a noninvasive signal of neutrophil-driven inflammation, making it a valuable first-line test for distinguishing IBD from IBS and for monitoring disease activity.

How the Test Is Done

The test requires a small stool sample that you collect at home using a provided kit. It is noninvasive and generally painless. For best results, collect the sample during an active symptomatic period, as calprotectin levels can fluctuate. Avoid testing right after a colonoscopy or during acute gastrointestinal bleeding, as these can skew results. Always inform your healthcare provider about any medications you are taking, especially NSAIDs or antibiotics.

Fecal Calprotectin Levels: Normal, Borderline, and High Ranges

While reference ranges can vary slightly by laboratory, most use the following general cutoffs:

• Normal (low): < 50 µg/g — suggests no significant intestinal inflammation.
• Borderline (moderate): 50–200 µg/g — may indicate mild inflammation or be influenced by other factors.
• High: > 200 µg/g — more likely significant inflammation warranting further evaluation.

However, a single value should never be interpreted in isolation. Your clinician will consider your symptoms, medical history, and other test results. For example, a calprotectin level of 150 µg/g in a person with bloody diarrhea is more concerning than the same level in someone with mild bloating.

What Is a Concerning Level of Calprotectin?

Generally, levels above 200 µg/g are considered high and are associated with a greater likelihood of IBD or other inflammatory conditions. Some studies suggest that levels above 150 µg/g in symptomatic patients may warrant further investigation, but thresholds can be age-dependent. If your result is above 200 µg/g, your doctor may recommend a colonoscopy to visually inspect the colon and take biopsies.

What Causes High Fecal Calprotectin?

Elevated calprotectin is most commonly associated with inflammatory bowel disease, but it is not specific to IBD. Several conditions and factors can raise your levels:

• Crohn's disease and ulcerative colitis (IBD)
• Infectious colitis (bacterial, viral, or parasitic)
• Microscopic colitis
• Use of NSAIDs (like ibuprofen) or proton pump inhibitors
• Recent colonoscopy or bowel preparation
• Intense exercise
• Colorectal cancer or other tumors
• Autoimmune diseases, such as rheumatoid arthritis or lupus
• Celiac disease or food allergies (in some cases)

It's important to note that high calprotectin does not always mean cancer. In fact, most people with elevated levels have a benign or treatable cause. However, because colorectal cancer can cause inflammation, your doctor may consider this as a possibility, especially if you have other risk factors or symptoms like blood in stool or unexplained weight loss.

Can You Have High Calprotectin Without IBD?

Yes. As listed above, infections, medications, and even vigorous exercise can temporarily raise calprotectin. For some people, a high level may be a false positive without any ongoing disease. This is why repeat testing and clinical correlation are essential. A single elevated result does not confirm IBD; it simply indicates that further investigation is warranted.

What Does a Borderline Calprotectin Level Mean?

A borderline result (50–200 µg/g) is a gray zone that can be challenging to interpret. It may indicate mild inflammation, but it can also be caused by non-inflammatory factors. Some laboratories use narrower ranges (e.g., 50–120 µg/g) for borderline, so always check the reference range on your report. If your level is borderline, your doctor may recommend:

1. Repeat the test during a symptomatic period to see if levels rise.
2. Review any medications that could affect results (e.g., NSAIDs, PPIs).
3. Check stool for infections to rule out gastroenteritis.
4. Consider additional blood tests like CRP or ESR.
5. If symptoms persist, a colonoscopy may be considered even with borderline levels.

The key is to interpret borderline values in the context of your overall clinical picture. For example, a borderline level in a young, otherwise healthy person with mild IBS-like symptoms may not require invasive testing, while the same level in an older adult with unintentional weight loss may prompt more urgency.

Calprotectin and IBD: How High Is Indicative of Crohn's or Colitis?

Levels above 200 µg/g are often considered suggestive of active IBD, especially if accompanied by typical symptoms. However, there is no single 'cutoff' that confirms a Crohn's or ulcerative colitis diagnosis. In clinical practice, a calprotectin level greater than 150–200 µg/g in a symptomatic patient significantly increases the likelihood of IBD, but the diagnosis is confirmed through endoscopy with biopsy. In addition, calprotectin levels can help differentiate IBD from IBS: in IBS, calprotectin is usually normal (<50 µg/g), while in IBD it is typically elevated.

When to Worry About Calprotectin and Consider a Colonoscopy

You should discuss with your clinician whether a colonoscopy is appropriate if your calprotectin is significantly elevated (e.g., >200 µg/g) and you have any of the following:

• Persistent diarrhea, especially if bloody or nocturnal
• Unexplained abdominal pain or cramping
• Unintentional weight loss
• Fever or night sweats
• Family history of IBD or colorectal cancer
• Age over 50 (due to increased colorectal cancer risk)

A colonoscopy is the gold standard for visualizing the colon and taking tissue samples. It can confirm or rule out IBD, microscopic colitis, and colorectal cancer. If your calprotectin is borderline but symptoms are severe or persistent, your doctor may still recommend a colonoscopy based on clinical judgment.

Factors That Can Falsely Elevate Calprotectin

False positives are relatively common. Common causes include:

• Recent use of NSAIDs (ibuprofen, naproxen)
• Proton pump inhibitors (omeprazole, esomeprazole)
• Acute infectious gastroenteritis
• Heavy exercise within 24 hours before the test
• Recent colonoscopy or bowel preparation
• Age (infants and young children naturally have higher levels)

To minimize false elevations, avoid NSAIDs for a few days before the test if possible, and inform your doctor about any other medications. If your result is unexpectedly high, repeating the test after addressing these factors may provide a more accurate picture.

How Fecal Calprotectin Compares to Other Markers

Fecal calprotectin is one of several biomarkers used in gut health. Here's how it fits in:

• CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate): blood tests that measure systemic inflammation, but they are not specific to the gut.
• Lactoferrin: another stool marker of inflammation, but calprotectin is more widely studied and stable.
• Fecal occult blood test: detects hidden blood, but not specific to inflammation.
• Gut microbiome tests: assess microbial composition and function, complementing calprotectin by revealing potential underlying dysbiosis.

No single marker is perfect; a combination of symptoms, blood tests, stool tests, and imaging often gives the clearest picture.

The Role of the Gut Microbiome in Calprotectin Elevations

The gut microbiome significantly influences mucosal immunity. An imbalance in gut bacteria (dysbiosis) can promote inflammation and potentially increase calprotectin levels. For example, a decrease in beneficial butyrate-producing bacteria (like Faecalibacterium prausnitzii) and an increase in pro-inflammatory microbes (like certain Proteobacteria) can compromise the gut barrier and stimulate immune cells.

How Microbiome Testing Adds Insight

A microbiome test can reveal whether your gut microbial community supports a healthy barrier and anti-inflammatory environment or if it is skewed toward dysbiosis. This information can help explain why your calprotectin might be elevated and guide targeted dietary or lifestyle strategies to support gut health. However, microbiome testing is not a diagnostic tool for IBD; it is a complementary assessment that should be interpreted alongside clinical data.

Practical Steps to Take After Your Calprotectin Result

Regardless of your calprotectin level, here are some general steps to consider:

1. Schedule a follow-up with your healthcare provider to interpret the result in context.
2. Prepare a symptom diary noting when symptoms occur, their severity, and any triggers.
3. Review your medication list with your doctor, especially NSAIDs and PPIs.
4. If your level is elevated, ask if a repeat test during a symptomatic period is recommended.
5. Discuss whether a colonoscopy or other imaging is appropriate based on your symptoms and risk factors.
6. Consider a microbiome test to gain insight into the microbial factors that might be contributing to inflammation.

Frequently Asked Questions

What is an alarming level of fecal calprotectin?

An alarming level is generally above 200 µg/g. This indicates significant intestinal inflammation and warrants prompt evaluation, typically with a colonoscopy. Levels above 500 µg/g are even more concerning and strongly suggest IBD.

What calprotectin level indicates Crohn's disease?

There is no definitive cutoff, but levels above 200 µg/g are commonly associated with active Crohn's disease. In practice, the higher the level, the more likely the presence of IBD. Diagnosis requires endoscopy and biopsy.

What cancers cause high calprotectin?

Colorectal cancer is the most common cancer associated with elevated calprotectin, but it is not a cancer test. Elevated levels can also occur with other gastrointestinal tumors. However, most people with high calprotectin do not have cancer; the test is a marker of inflammation, not malignancy.

Is calprotectin a tumor marker?

No, calprotectin is not a tumor marker. It is a marker of inflammation. However, colorectal cancer can cause inflammation, so elevated calprotectin may prompt further investigation to rule out cancer, but it is not used as a direct cancer screening test.

Can food cause high calprotectin?

Food itself is not a direct cause of high calprotectin, but food allergies or intolerances (like celiac disease) can lead to intestinal inflammation and elevated levels. Additionally, a diet high in processed foods may contribute to gut dysbiosis, which can indirectly promote inflammation.

Can stress or exercise affect calprotectin?

Intense exercise has been shown to temporarily raise calprotectin levels. Chronic stress may also influence inflammation through immune pathways, though the direct effect on calprotectin is less clear. If your result is unexpectedly high, consider whether you exercised heavily before the test.

How long does it take for calprotectin to normalize after treatment?

This varies depending on the underlying cause and treatment. For infections, levels may return to normal within weeks. For IBD, normalization can take months with effective therapy. Your doctor will advise on repeat testing intervals.

Key Takeaways

• Fecal calprotectin is a noninvasive marker of gut inflammation that helps distinguish IBD from IBS.
• Normal is <50 µg/g, borderline is 50–200 µg/g, and high is >200 µg/g, but thresholds vary by lab.
• High calprotectin can be caused by IBD, infections, medications, and even cancer, but is not always serious.
• Borderline results require clinical correlation and repeat testing before deciding on invasive procedures.
• Colonoscopy is warranted when calprotectin is high and symptoms are concerning.
• Microbiome testing can add insight into the underlying microbial factors contributing to inflammation.
• Always discuss results with a healthcare provider for an accurate interpretation.

Explore Related Gut Health Insights

If you're interested in understanding your gut health on a deeper level, consider a microbiome test to see how your microbial balance may be influencing inflammation. Longitudinal tracking through a gut health membership can help you monitor changes over time. For clinicians and organizations, InnerBuddies also offers a platform for partners to integrate these insights.