Calprotectin

When you have inflammation in your intestines, your immune system sends certain types of white blood cells (neutrophils) to the inflamed area. As these cells move into the gut, they release calprotectin, which then shows up in your stool. Inflammation in your intestines can cause severe watery or bloody diarrhea with abdominal (belly) pain and/or cramping that last for more than a few days.

A calprotectin test can find out whether your intestinal condition involves inflammation. But it can't diagnose the specific cause — it tells you inflammation is present without pointing to which condition is causing it.

Calprotectin levels are usually grouped into three ranges that help your provider decide what to do next.

A result under about 50 mcg/g is normal and makes inflammatory bowel disease (such as Crohn's disease or ulcerative colitis) unlikely. If your symptoms continue, your provider may look into non-inflammatory causes such as irritable bowel syndrome.

A result in the borderline zone of about 50 to 120 mcg/g can show up with low-level gut inflammation, well-controlled IBD, or regular use of pain relievers like ibuprofen, naproxen, or aspirin. If your symptoms still suggest IBD, a repeat test in roughly a month or two is often the next step.

A result above about 120 mcg/g points to active inflammation in the gut. The higher the number, the more inflammation is likely. Common causes include inflammatory bowel disease, gut infections, and sometimes colorectal cancer or celiac disease. More tests, such as a colonoscopy, are often the next step.

Calprotectin tells your provider that there is inflammation in the digestive tract, but not exactly where it is or what is causing it. Other tests are needed to find the exact cause.