Gut health
What Does a Fecal Calprotectin Test Result Mean?
A number under 50 doesn't rule out every gut problem, and a number over 200 doesn't name the one you're worried about. What the test can and can't tell apart matters more than the cutoff printed on the page.
The short answer
Fecal calprotectin measures neutrophil activity in the gut lining, not a specific disease. A result under roughly 50 µg/g makes inflammatory bowel disease unlikely and supports a working diagnosis of irritable bowel syndrome without colonoscopy. A result above about 150-200 µg/g signals gut inflammation needing further investigation to find its cause, which can be Crohn's disease, ulcerative colitis, an infection, NSAID-related damage, or something else. The test flags inflammation; it does not identify what caused it.
What this actually measures
Calprotectin is a protein released by neutrophils, a type of white blood cell that accumulates wherever the intestinal lining is inflamed. The test measures its concentration in a stool sample as an indirect marker of neutrophil activity in the gut wall - it detects that inflammation is present, not what is causing it.
| Band | Value | What it depends on |
|---|---|---|
| Inflammation unlikely | Below roughly 50 µg/g | The cutoff most commonly used by lab assays, though some labs set normal as high as 100 µg/g - check the range printed on your own report rather than this one. |
| Borderline | Roughly 50-150 µg/g | Often prompts a repeat test after a few weeks rather than immediate referral, since a single stool reading has real day-to-day variation. |
| Elevated | Above roughly 150-200 µg/g | The level that typically prompts referral for further investigation; the exact number used depends on the lab's assay and on the patient's age. |
What the test is actually measuring
Calprotectin is not a hormone or a nutrient. It’s a protein carried inside neutrophils, the white blood cells that arrive first at a site of tissue damage or infection. When the intestinal lining is inflamed, neutrophils move into the gut wall in larger numbers, some of them break down there, and calprotectin leaks into the gut and out in stool.
The test measures how much of it shows up in a stool sample. That’s the entire mechanism. It doesn’t look at the colon, it doesn’t identify a specific pathogen, and it can’t tell Crohn’s disease apart from ulcerative colitis or a bad stomach bug. It answers one narrower question: is there active, neutrophil-driven inflammation somewhere in the gut right now, and roughly how much.
That narrowness is the source of both its usefulness and its most common misreading. A high number is a real finding. It is not, by itself, a diagnosis.
Reading the number on your own report
Labs don’t share a single universal cutoff, which is one of the more frustrating things about this test if you’re trying to match your result to something you read online. The pattern most reports follow looks roughly like this:
| Result | What it usually suggests | What tends to happen next |
|---|---|---|
| Below ~50 µg/g | Inflammation unlikely | Often no further gut-specific testing on this basis alone |
| ~50-150 µg/g | Borderline / equivocal | A repeat test after a few weeks is common, rather than immediate referral |
| Above ~150-200 µg/g | Elevated | Usually prompts referral for further investigation, such as colonoscopy |
Two things are worth noticing here. First, the bands genuinely overlap between labs: some report normal as anything under 50, others use 100, and the “elevated” threshold at one clinic can sit close to the “borderline” ceiling at another, because different assay types don’t produce numerically identical results from the same sample. Second, a single stool sample carries real day-to-day noise, which is exactly why a borderline reading is usually re-tested rather than acted on immediately.
If your own lab printed a reference range on your report, treat that range as the authority, not a number pulled from an article.
Where the test is genuinely strong: ruling things out
The clearest, best-supported use of fecal calprotectin is negative. A low result is good evidence against the kind of gut inflammation that Crohn’s disease and ulcerative colitis produce. NICE, the UK’s clinical guidance body, recommends the test specifically to help decide which adults with new lower gastrointestinal symptoms need referral for further gut investigation, rather than sending everyone with possible IBS symptoms straight to colonoscopy.
That’s a genuinely useful clinical tool, and it’s the honest reason the test gets ordered as often as it does: it spares a meaningful number of people an invasive procedure they didn’t need.
Reading a high result is harder, because the same neutrophil response shows up whether the underlying cause is Crohn’s disease, ulcerative colitis, a gut infection, NSAID-related injury, diverticulitis, or, less commonly, a colorectal polyp or tumor. A raised number tells you inflammation is present. It does not tell you which of those is responsible, and that gap is exactly why the usual next step after a high result is an endoscopic look, not a second stool test.
Calprotectin in the IBS-versus-IBD decision
This is the comparison most people searching for this test actually want answered, so it’s worth being direct about the logic. Irritable bowel syndrome, by definition, does not involve the mucosal inflammation that raises calprotectin — it’s a disorder of gut function and sensation rather than gut tissue damage. That’s the whole basis for using the test as a triage step: someone with IBS-pattern symptoms (cramping, an altered bowel habit, bloating) and a low calprotectin result has real evidence pointing away from Crohn’s disease or ulcerative colitis, without needing a colonoscopy to establish that.
It works as a rule-out tool, not a rule-in one, and it works best in the population it was designed for: adults with recent-onset lower gastrointestinal symptoms where cancer isn’t already suspected on other grounds. Someone with red-flag symptoms — rectal bleeding, unexplained weight loss, a strong family history of bowel disease — needs referral regardless of what a calprotectin result shows, because those symptoms carry their own threshold for investigation that a stool marker doesn’t override.
What else moves the number, besides IBD
A raised result outside of Crohn’s disease or ulcerative colitis is common enough that it shouldn’t automatically be read as pointing toward inflammatory bowel disease. The gut inflames for a number of reasons:
- NSAID use. Regular ibuprofen, aspirin, or naproxen use can injure the gut lining directly and raise calprotectin independent of any underlying bowel disease, which is worth mentioning to whoever ordered the test if you take these regularly.
- Infection. A recent or ongoing gastrointestinal infection produces much the same neutrophil response that IBD does, which is part of why testing is usually timed away from an obvious stomach bug.
- Diverticulitis. Inflamed diverticula in the colon wall raise calprotectin through the same underlying mechanism as IBD.
- Polyps and colorectal cancer. A less common cause, but part of why a persistently elevated result doesn’t get dismissed without a look.
None of this makes the test unreliable. It makes a high result a prompt for further investigation rather than an answer on its own.
Age changes what the number means
A calprotectin level that would be striking in an adult can be unremarkable in an infant. Young children run physiologically higher calprotectin than adults, likely reflecting a gut barrier that is still maturing, and pediatric reference ranges reflect that by sitting higher across the board. Comparing a child’s raw number against an adult cutoff will make a healthy toddler look inflamed on paper. This is one of the test’s real limits, and it’s the one most often missed when people compare results online without checking whose reference range they’re actually using.
Used after diagnosis, not only before it
Fecal calprotectin isn’t only a triage tool at the start of an investigation. In people already diagnosed with Crohn’s disease or ulcerative colitis, repeated calprotectin testing over time helps track whether the gut lining is actively inflamed, which correlates reasonably well with what a colonoscopy would show, without needing a scope every time a clinician wants to check on treatment response or catch a flare early. It functions there as a monitoring instrument alongside symptoms and other markers, not as a replacement for the endoscopic exam that established the diagnosis in the first place.
The honest limits of this test
Two things are worth stating plainly rather than smoothing over. First, cutoffs are not standardized: the number your lab calls “elevated” is a property of its particular assay, not a fixed biological line, which is why comparing your result against a figure from a different lab or a different country can mislead more than it clarifies. Second, a single stool sample carries meaningful day-to-day variability, so one borderline reading is a data point, not a verdict — retesting is the normal, expected response, not a sign the first test failed.
Set against that, the core use case holds up well: a low result arguing against inflammatory bowel disease in someone with new gut symptoms rests on solid reasoning, since neutrophilic inflammation is close to a defining feature of IBD and IBS doesn’t produce it. Where the reasoning gets weaker is in treating any single elevated number as a diagnosis in itself, rather than as a reason to look further and find out which of several possible causes actually produced it.
When to stop reading and see someone
A result above roughly 150-200 µg/g, or any result alongside rectal bleeding, unexplained weight loss, iron-deficiency anemia, persistent night-time diarrhea, or a family history of inflammatory bowel disease or colorectal cancer, is a reason to see a doctor about referral for colonoscopy, not a reason to simply repeat the stool test at home.
Questions we get
What is a normal fecal calprotectin range?
There isn't one universal number, because different labs use different assays with different cutoffs. Many report anything under about 50 micrograms per gram of stool as normal, some set that line at 100, and a result labeled 'borderline' usually falls somewhere between the normal cutoff and around 150. The reference range printed on your own lab report matters far more than any figure quoted in an article, this one included.
Can a fecal calprotectin test tell IBS from IBD?
That's one of the main reasons the test gets ordered. Irritable bowel syndrome does not produce the mucosal inflammation that releases calprotectin, while Crohn's disease and ulcerative colitis usually do, so a low result in someone with typical IBS-pattern symptoms makes inflammatory bowel disease unlikely enough that a colonoscopy can often be avoided on that basis. A high result points the opposite way, toward inflammation and further investigation, though it does not say which condition is causing it.
What can cause high calprotectin levels other than IBD?
Calprotectin rises with any process that draws neutrophils into the gut lining, not only Crohn's disease or ulcerative colitis. Gastrointestinal infections, regular use of NSAID painkillers such as ibuprofen or aspirin, diverticulitis, and colorectal polyps or cancer can all raise the number, which is why an elevated result functions as a reason for further testing rather than as a diagnosis by itself.
Does age affect fecal calprotectin results?
Yes, and it's one of the test's real limitations. Infants and young children run naturally higher calprotectin levels than adults, likely reflecting a gut barrier that is still maturing, so a number that would be striking in an adult can be unremarkable in a toddler. Pediatric reference ranges sit higher than adult ones across the board, and a child's result should be read against a pediatric range rather than the adult cutoffs quoted for grown-up patients.
Where the figures came from
- NICE - Faecal calprotectin diagnostic tests for inflammatory diseases of the bowel (DG11) — Fecal calprotectin testing is recommended to help decide which adults with recent-onset lower gastrointestinal symptoms need referral for further investigation of possible inflammatory bowel disease, rather than referring everyone straight to colonoscopy
- MedlinePlus - Fecal Calprotectin Test — What the fecal calprotectin test measures, how the stool sample is collected, and how results are generally used
- NHS - Crohn's Disease: Diagnosis — Fecal calprotectin is used as a non-invasive step to help decide who needs further investigation for Crohn's disease before proceeding to colonoscopy
Lena Naumovska
Editor responsible for micronutrients and gut health
Lena edits the micronutrients and gut sections. She is unusually interested in dose, timing and absorption, because those decide whether a supplement does anything and they are the parts most articles skip. She is not a clinician or a dietitian. Where the evidence for a claim is thin she grades it thin rather than rounding it up, which makes some of these entries shorter and duller than the competition's.
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