Specialty Testing Guide › GI-MAP Gut Testing
Fecal calprotectin is a protein released by white blood cells called neutrophils. When the lining of the bowel is inflamed, neutrophils move into it and calprotectin spills into the stool, so a stool level reflects how much inflammation is present. It is the best-studied marker on a GI-MAP report.
Its main job in medicine is triage: helping tell inflammatory bowel disease (IBD), such as Crohn's disease and ulcerative colitis, apart from irritable bowel syndrome (IBS), which does not inflame the bowel lining. A normal result makes IBD unlikely. A high result is a reason for a proper medical workup, not a supplement plan.
Key takeaways
- Calprotectin is a well validated stool marker of bowel inflammation and is widely used to separate IBD from IBS.
- A low result is reassuring because it rarely misses IBD in adults, while a high result has several possible causes.
- Painkillers such as ibuprofen and acid-reducing medicines can push the number up.
- A clearly or persistently high result, or any result with alarm symptoms, calls for a gastroenterologist.
Why calprotectin is trusted
Unlike many functional stool markers, calprotectin has been tested against colonoscopy in many studies. In a meta-analysis of adult studies, calprotectin had a pooled sensitivity of 93% and specificity of 96% for detecting IBD.1
The same analysis estimated that using the test first would cut the number of adults needing endoscopy by 67%, at the cost of a delayed diagnosis in about 6% of adults because of false negatives.1 So the test is very good, but not perfect, and symptoms still matter.
US gastroenterology guidance builds on this. The American College of Gastroenterology suggests checking fecal calprotectin in people with suspected IBS and diarrhea to rule out IBD.2 If you have been told you have IBS, see the clinic's page on IBS in Philadelphia.
Cutoffs: why the numbers differ
There is no single universal cutoff. Calprotectin is measured with antibody-based kits, and different labs use different assays and different reference limits.
- Many diagnostic studies use cutoffs of 50 or 100 micrograms per gram of stool. A review of primary care and outpatient studies found no significant difference in accuracy between those two cutoffs.3
- The GI-MAP sample report lists its reference as under 173 micrograms per gram.4
Because of these differences, compare a result with the range printed on your own report and, if you are retested, try to use the same lab. A number from one lab is not directly comparable with another lab's.
What a normal result tells you
A normal calprotectin is one of the more reassuring results on a stool panel. In that same review, assuming organic gut disease affected 1% of people tested, the negative predictive value was 100% and the positive predictive value only 4.2%.3
In plain terms, when IBD is uncommon in the group being tested, a low calprotectin almost always means no inflammatory bowel disease or similar organic disease, while a high one is often a false alarm. That is why a high result calls for further testing rather than a diagnosis.
Causes of a high result besides IBD
The lab's interpretive guide lists intestinal infections, certain drugs including NSAIDs, polyps, diverticulitis and colorectal cancer among possible causes of raised calprotectin, alongside IBD.5
- Medicines. In a study of people with IBS or similar functional bowel disorders, those with recent proton pump inhibitor prescriptions had calprotectin levels of 66 versus 23 micrograms per gram in those without, and NSAID users showed a similar rise.6
- Infection. A gut infection can raise calprotectin.
- Other bowel conditions. Polyps, diverticulitis and cancer can all raise it, which is why a high result is not something to treat at home.
Tell your clinician about every medicine and supplement you take, including over-the-counter painkillers. Do not stop a prescribed medicine to change a test result without speaking to the prescriber.
When a high result needs a gastroenterologist
See a doctor promptly, and expect a referral to a gastroenterologist, if calprotectin is clearly high or stays high, or if it comes with any of these:
- Blood in the stool or black stools
- Unintended weight loss
- Anemia or iron deficiency
- Diarrhea that wakes you at night or lasts for weeks
- A family history of IBD or colorectal cancer
A stool panel is not colorectal cancer screening, and a normal calprotectin does not replace a colonoscopy when one is due. Our article on GI-MAP vs colonoscopy covers the screening side.
Is a GI-MAP the right test for you?
If your main question is whether you have IBD, a standalone calprotectin ordered by your doctor or gastroenterologist answers it directly. A broader panel makes more sense when IBD is not the main concern and you and your clinician want a wider view of the gut. Before booking, read who should not book a GI-MAP, and see the GI-MAP hub for the rest of this guide.
Frequently asked questions
Does a high calprotectin mean I have Crohn's disease or colitis?
No. It means there is likely inflammation somewhere in the bowel. Infections, medicines and other conditions can cause it, so a gastroenterologist decides on next steps, which often include colonoscopy.
My calprotectin was borderline. What now?
Talk with your clinician about medicines that may have raised it, recent illness and your symptoms. Ask whether a repeat test makes sense, ideally from the same lab.
Can diet lower my calprotectin?
If the cause is IBD, diet changes should not replace medical treatment or delay care. If the cause was a passing infection or a medicine, the level may settle once that resolves.
Related reading
This article is for general education and is not medical advice. Decisions about testing and treatment should be made with your clinician. If you have severe symptoms, call 911. For a suspected poisoning, call Poison Control at 1-800-222-1222.
