Calprotectin vs CRP for UC: Which One Reflects Colon Inflammation Better?
Last Updated Jan 15, 2026
Ulcerative colitis (UC) causes ongoing inflammation in the lining of the colon and rectum. During diagnosis and follow-up, clinicians often track “inflammation markers” to understand whether symptoms are coming from active gut inflammation or something else. Two of the most common options are fecal calprotectin (a stool test) and C-reactive protein (CRP, a blood test). They can both be useful, but they measure different things, so results do not always match symptoms or each other.
Fecal calprotectin: a stool marker that often reflects colon inflammation
Fecal calprotectin is measured in a stool sample. Calprotectin comes from white blood cells that gather when there is inflammation in the intestines, so higher levels can suggest inflammation in the gut rather than inflammation somewhere else in the body. Many care teams use it as a noninvasive way to check for intestinal inflammation and to help predict when disease may be active. [1]
When comparing calprotectin vs CRP in ulcerative colitis, fecal calprotectin often reflects colon inflammation more directly because it comes from the intestinal tract itself. Clinical guidelines note that fecal calprotectin levels tend to correlate with inflammation seen during endoscopy (a camera exam of the colon) and under the microscope on biopsy, and it is commonly used to monitor disease activity or possible relapse. [2]
That said, fecal calprotectin is still a marker, not a perfect “yes or no” test. Levels can vary from day to day, and they can rise for reasons other than UC, such as some infections or other causes of irritation in the gut. This is one reason many clinicians focus on trends over time, along with symptoms and other tests, rather than a single result.
CRP and ESR: blood markers of whole-body inflammation, plus how clinicians interpret trends
CRP is a protein made by the liver in response to inflammation. A CRP test measures inflammation somewhere in the body, but it cannot pinpoint where the inflammation is coming from. Erythrocyte sedimentation rate (ESR, sometimes called “sed rate”) is another blood test that indirectly measures inflammation by looking at how quickly red blood cells settle in a tube. Both CRP and ESR can rise with many conditions, including infections and autoimmune diseases, so they are not specific to UC. [3]
In crp ulcerative colitis monitoring, CRP can be helpful, especially when UC is more severe or more extensive. But CRP (and ESR) can sometimes be normal even when UC inflammation is present, particularly in mild or more limited disease. Expert consensus statements also note that fecal calprotectin is an accurate marker of colonic inflammation, while CRP and ESR are useful for monitoring response in severe colitis, and none of these markers can fully separate UC from other causes of colitis on their own. [4]
Reasons fecal calprotectin vs CRP may not match symptoms include:
- Symptoms caused by noninflammatory issues (for example, functional bowel symptoms, stress, diet changes)
- Inflammation that is present but causing few symptoms (sometimes called “silent” inflammation)
- Inflammation in other parts of the body raising CRP, even if the colon is calmer
- Timing, because biomarkers can rise and fall at different speeds
For monitoring UC labs, many clinicians use a “bigger picture” approach: symptoms plus biomarkers, repeated over time. The American Gastroenterological Association (AGA) recommends strategies that combine symptoms with biomarkers for monitoring, and it outlines how stool markers (like fecal calprotectin) and blood markers (like CRP) can help rule in or rule out active inflammation in certain situations, sometimes guiding whether endoscopy is needed. [5]