Calprotectin is one of the few stool markers that speaks directly to intestinal inflammation rather than inferring it. Most functional stool markers describe microbial populations or digestive capacity. Calprotectin measures a protein released by immune cells at the site of inflammation, which is what makes it useful early in a workup.
That specificity matters because gastrointestinal presentations overlap. Loose stools, cramping, urgency, and bloating look similar across inflammatory bowel disease, irritable bowel syndrome, viral infection, and food sensitivity reactions. Calprotectin helps separate inflammatory from non-inflammatory patterns before a treatment plan is built.
This post covers what calprotectin is, what each result range indicates, which conditions it is associated with, what can distort a result, and how practitioners approach elevated levels clinically.
Calprotectin is a calcium-binding protein released by neutrophils, monocytes, and reactive macrophages. When the intestinal mucosa is inflamed, these immune cells migrate into the gut and the protein is shed into the stool.
Two properties make it practical as a stool marker:
Calprotectin is measured on the US BioTek™ GI Standard Profile and GI Advanced Profile as part of the GIT Functional Markers section. It is not included on the GI Basic Profile, which covers PCR microbiome identification only.
Calprotectin is reported in micrograms per gram of stool. US BioTek's reference range is under 50.0 µg/g, and results are interpreted across three bands.
Levels above 200 µg/g are associated with active inflammatory bowel disease and gastrointestinal inflammation. Elevation may also occur due to bacterial infection, colitis, or, less commonly, cancer. Calprotectin should be reassessed after about four weeks for confirmation, since a single elevated result does not distinguish a transient inflammatory event from ongoing disease activity.
This band is an indicator of chronic inflammation. Inflammation at this level may reflect inflammatory bowel disease in remission, or inflammation caused by non-steroidal anti-inflammatory drugs. As with high results, levels should be reassessed after about four weeks.
Low calprotectin is usually associated with viral gastrointestinal infections or non-inflammatory bowel conditions such as irritable bowel syndrome. A low result in a symptomatic patient is clinically useful information: it points the workup away from an inflammatory driver and toward motility, digestion, microbiome composition, or food sensitivity.
| Range | Result band | Most commonly associated with | Follow-up |
|---|---|---|---|
| Below 50 µg/g | Low | Viral GI infection, non-inflammatory conditions such as IBS | Investigate non-inflammatory drivers |
| 50 to 200 µg/g | Moderate | Chronic inflammation, IBD in remission, NSAID-driven inflammation | Reassess after about 4 weeks |
| Above 200 µg/g | High | Active IBD, GI inflammation, bacterial infection, colitis, occasionally cancer | Reassess after about 4 weeks for confirmation |
Clinical case contributed by Dr. Rachel Onah BSc. ND MRN. Patient details have been limited to protect identity.
A 54-year-old woman with a long-standing history of inflammatory bowel disease, specifically Crohn's disease, was interested in changing her treatment plan. She had been receiving infliximab, a biologic medication used to control inflammation in moderate to severe IBD, but wanted to discontinue biologic therapy and transition to prednisone and mesalamine.
The patient maintained a health-conscious lifestyle and followed a paleolithic-style diet. Because she wanted additional information about her intestinal health before making a medication change, a GI Advanced Profile was performed to evaluate markers associated with intestinal inflammation, gastrointestinal function, and the gut microbiome.
One of the important considerations in inflammatory bowel disease is that symptoms alone do not always tell the full story. A patient may feel relatively well while underlying intestinal inflammation persists.
In this case, the GI Advanced Profile provided additional information that raised concern about ongoing intestinal inflammation. Calprotectin was elevated, and occult blood was also present in the stool, providing another important clinical finding that warranted consideration in the overall assessment.
The assessment also demonstrated several findings involving the patient's gastrointestinal environment, including:
The patient had hoped that the testing would support discontinuing infliximab and transitioning to prednisone and mesalamine. However, the results did not provide reassurance that inflammation was adequately controlled.
Given the patient's history of Crohn's disease and the evidence suggesting ongoing intestinal activity, the clinical decision was to continue infliximab rather than discontinue biologic therapy. The primary goal was to maintain control of intestinal inflammation and avoid making a medication change based solely on symptoms or the patient's desire to reduce her medication burden.
Care also focused on addressing the elevated levels of Klebsiella species and Citrobacter species, which may be associated with intestinal dysbiosis and could potentially contribute to impaired intestinal barrier function and elevated zonulin levels. In addition, supportive naturopathic interventions, including omega-3 fatty acids, curcumin, and Boswellia, were recommended as part of a comprehensive approach to help support a healthy inflammatory response.
Calprotectin is a marker of intestinal inflammation, not a marker of a specific disease. Interpretation depends on the level and on the rest of the clinical picture. The conditions associated with elevated results include:
Calprotectin is also used in the other direction. Because low levels are usually associated with viral infections or non-inflammatory bowel conditions such as IBS, the marker supports clinical assessment of whether an inflammatory process is present at all.
A calprotectin value is only as useful as the context around it. Several factors can raise or suppress a result independent of intestinal inflammation.
May elevate calprotectin:
May suppress an expected elevation:
This is the practical reason to collect a full medication history alongside the sample. A normal calprotectin in a patient on immunosuppressants does not carry the same meaning as a normal calprotectin in an untreated patient.
Calprotectin is reported next to the other GIT Functional Markers: pancreatic elastase, secretory IgA, zonulin, beta-glucuronidase, steatocrit, and anti-gliadin IgA. Because all parts of the digestive system are interconnected, one change in a patient's homeostasis may affect multiple biomarkers at once.
Patterns worth reading together:
The interpretive principle is to consider the test as a whole. Calprotectin tells you inflammation is present and roughly how active it is. The surrounding markers help explain why.
Calprotectin is a downstream measurement. Levels change when the underlying inflammation changes, so the clinical work is directed at the driver rather than at the number. The interventions below are drawn from the patient support and gut restoration sections of the GI Profile Stool Results Interpretation Guide and are applied at the practitioner's discretion.
Modification of diet and alteration of the consistency of fibrous foods may provide symptom relief and play a role in patient support during active disease. Fiber tolerance can be improved through texture modification to decrease bloating and gas:
Once fruits and vegetables are tolerated, a similar texture modification program can be considered for legumes. Human studies indicate that either a Mediterranean diet or a moderate-protein, plant-rich Paleo diet can maintain gut microbiome diversity.
Both high and moderate calprotectin results should be reassessed after about four weeks. A single value establishes that inflammation is present. A second value establishes whether the intervention is working.
Follow-up on the case above, contributed by REPLACE-AUTHOR-NAME.
After six months of continued therapy and targeted gastrointestinal support, the patient demonstrated a significant improvement in objective and subjective markers of intestinal health. Her fecal calprotectin decreased to 46.2 µg/g, indicating substantially lower intestinal inflammatory activity compared with her initial assessment.
The patient also reported a noticeable reduction in gastrointestinal symptoms, including abdominal pain, burning, gas, and cramping. Together, the improvement in calprotectin and reduction in symptoms suggested better overall control of her Crohn's disease and supported the decision to continue her current therapeutic approach.
| Marker | Baseline | Six months | Reference |
|---|---|---|---|
| Calprotectin | Above 2000 µg/g (high) | 46.2 µg/g | Under 50.0 µg/g |
| Secretory IgA | 298 ng/mL (low) | 619 ng/mL | 510 to 2040 ng/mL |
| Occult blood | Positive | Negative | Negative |
| Anti-transglutaminase IgA | 36.0 µg/g | 1.0 µg/g | Under 100.0µg/g |
Calprotectin is measured on a stool sample as part of the GI Standard Profile and the GI Advanced Profile. Both profiles report it in the GIT Functional Markers section alongside the other digestive and immune markers, so the result arrives in context rather than in isolation.
The GI Advanced Profile adds culture and antimicrobial sensitivities for live yeast, pathogens, and dysbiotic bacteria. Where an elevated calprotectin sits next to an identified organism, sensitivities allow treatment to be directed rather than empirical, which is the current standard of care under antimicrobial stewardship principles.
Sample collection is designed for at-home use with minimal disruption to the patient's routine. As with any functional test, results are most meaningful when interpreted alongside patient history, symptoms, and the rest of the panel.
US BioTek brings more than thirty years of laboratory science to functional gastrointestinal testing, with calprotectin reported in full clinical context rather than as a standalone value.
What we offer:
Talk to our team to learn more about the GI Standard Profile and GI Advanced Profile and how to use them in your practice.
Calprotectin answers a narrow question well: is the intestinal mucosa inflamed, and how actively. Levels above 200 µg/g point toward active inflammatory disease and warrant confirmation. Levels between 50 and 200 µg/g indicate chronic inflammation that may reflect disease in remission or medication effect. Levels below 50 µg/g redirect the workup toward non-inflammatory causes. None of those bands is a diagnosis on its own, which is why calprotectin earns its place next to the digestive, barrier, and microbiome markers rather than ahead of them. For clinicians deciding whether to treat inflammation or investigate something else entirely, that distinction is where the workup starts.