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Fecal calprotectin: the at-home test that tells you if it's IBS or something else

Stool test tube and mailer box

A blood test can show that inflammation exists somewhere in the body, but it can't point to the gut specifically. Fecal calprotectin closes that gap. The protein is released by immune cells directly into the intestines during active inflammation, then passes out with stool, where a lab or a home test kit can measure it in micrograms per gram.[1]

IBS and inflammatory bowel disease can produce nearly identical symptoms: cramping, urgency, altered bowel habits. But IBS involves no measurable inflammation, while Crohn's disease and ulcerative colitis do. A normal calprotectin result makes IBD unlikely and supports an IBS diagnosis instead, and the test can even help someone avoid an unnecessary colonoscopy, according to the Cleveland Clinic.[1]

Under 50 µg/g
Typically within normal limits; also the stricter target doctors look for once someone with IBD is in remission.
50–150 µg/g
Usually low enough to help rule out active inflammation in someone believed to be in remission.
150–250 µg/g
Borderline or indeterminate; doctors often repeat the test at the same lab before deciding on next steps.
Over 500 µg/g
Substantially elevated and strongly associated with active disease.

Ranges from [2]. Different lab assays can produce two- to three-fold differences for the same stool sample, so trends across repeated tests matter more than any single number.

1. Collect. A small stool sample goes into the kit's provided container using the attached applicator, done at home.
2. Send or scan. Mail the sealed sample to a lab, or use a home reader such as IBDoc, a smartphone-based monitor built for IBD patients tracking flares between appointments.[3]
3. Result. The lab or reader reports a number in micrograms of calprotectin per gram of stool.
4. Interpret. A doctor weighs that number against reference ranges and, ideally, against your own past results.
A normal result doesn't rule out every gut condition, and an elevated one doesn't name which condition is causing it. The test screens for inflammation broadly; it doesn't replace a colonoscopy or imaging when those are still needed to reach a final diagnosis.

What to do with this

If a doctor orders this test for ongoing digestive symptoms, a result under 50 makes inflammatory bowel disease unlikely, and a workup for IBS or another functional cause is reasonable. A result above roughly 250 warrants further evaluation, and one in the borderline zone should be repeated at the same lab before concluding anything. If IBD is already confirmed, ask whether a home monitoring option exists through your clinic or a telehealth provider. Tracking calprotectin between flares can reduce how often an in-person visit is needed.

Sources:
  1. Cleveland Clinic, "Fecal Calprotectin Test"
  2. Aidy, "Fecal Calprotectin Results: What 50, 150, 250, and 500+ Can Mean"
  3. IBDoc by BÜHLMANN, home calprotectin monitoring

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