Calprotectin is a protein released by certain white blood cells, mainly neutrophils, when they move into the lining of the gut. A high level in a child’s stool almost always means one thing: there is inflammation somewhere in the intestinal tract. It does not tell you why the inflammation is there. That is the job of the next round of tests.
Because calprotectin is measured in stool, it reflects what is happening inside the bowel rather than somewhere else in the body. A single high result is a signal, not a diagnosis. Many children with high levels turn out to have a temporary infection or another treatable cause, and some have a chronic condition that needs long-term care.
What Is Calprotectin And Why Is It Measured?
Calprotectin makes up a large share of the proteins found inside neutrophils. When neutrophils gather in the gut wall during inflammation, they release calprotectin, and it passes into the stool. Measuring it is a non-invasive way to estimate how much inflammation is present in the intestines.
The test is used most often to help tell the difference between inflammatory bowel disease (IBD) and conditions that are not inflammatory, such as irritable bowel syndrome. It is also used to track disease activity in children already diagnosed with IBD. Because it is a stool test, it avoids the need for more invasive procedures in the first round of evaluation.
It is important to understand what calprotectin is not. It is not specific to any single disease. A high value tells a clinician that inflammation is likely present, but it does not identify the cause, the location, or the severity on its own.
What Causes High Calprotectin Levels In A Child?
The causes fall into a few broad groups: infections, inflammatory bowel disease, food-related reactions, and a range of other conditions that inflame the gut lining. In children, infection is one of the most common reasons for a temporarily high result.
Gastrointestinal infections are a frequent cause. Bacterial, viral, and parasitic infections can all inflame the intestinal lining and raise calprotectin. Levels often return toward normal after the infection clears, which is why doctors sometimes repeat the test weeks later rather than acting on a single reading.
Inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, is a major reason the test is ordered in the first place. In these conditions, chronic inflammation of the gut lining keeps calprotectin elevated. Children with IBD often have persistently high levels rather than a one-time spike.
Cow’s milk protein allergy and other food-protein allergies can inflame the gut in infants and young children and raise calprotectin. This is more common in the first years of life.
Other causes include:
- Celiac disease, an immune reaction to gluten that damages the small intestine
- Use of nonsteroidal anti-inflammatory drugs (NSAIDs), which can irritate the gut lining
- Untreated or severe intestinal infections
- Certain autoimmune conditions that affect the digestive tract
- Bleeding in the gut from various causes
In some children, a high result is found with no clear cause, and repeat testing shows it has returned to normal. This is one reason clinicians interpret a single value with care.
Can Infection Cause A High Calprotectin Level?
Yes. Infection is one of the most common causes of a high calprotectin level in children. When bacteria, viruses, or parasites inflame the lining of the gut, neutrophils move in and release calprotectin, which shows up in the stool.
This matters because it means a high result does not automatically point to IBD. A child with a recent bout of diarrhea and a high calprotectin may simply have had an infection. For this reason, many doctors repeat the test after the child has recovered. If the level falls, infection was likely the cause. If it stays high, further testing may be needed.
Some infections are more likely than others to raise the level. Invasive bacterial infections tend to cause more inflammation than mild viral ones. But the test cannot reliably tell which type of infection is present, so it is used alongside other information rather than on its own.
How Is Calprotectin Measured And What Do The Numbers Mean?
Calprotectin is measured from a small stool sample. The result is reported in micrograms per gram of stool (mcg/g). Reference ranges vary somewhat between laboratories, so the cutoff used by your child’s lab matters.
In general, levels below about 50 mcg/g are considered normal in adults and older children. Levels between roughly 50 and 200 mcg/g are often called borderline or mildly elevated. Levels above 200 mcg/g are more likely to reflect active inflammation.
These numbers are guides, not absolutes. Different labs use slightly different thresholds, and a value that is high in one lab may fall in a different category in another. Always read the result against the reference range printed on your child’s report.
It is also worth knowing that calprotectin can be mildly elevated for reasons that are not serious, and it can occasionally be normal even when inflammation is present. No single number replaces a full clinical picture.
What Symptoms Go Along With A High Calprotectin Level?
The symptoms depend on the underlying cause, not on the calprotectin number itself. A child with a mild infection may have only short-lived diarrhea. A child with IBD may have a pattern of symptoms that has been building for weeks or months.
Symptoms that often prompt testing include:
- Ongoing or recurring diarrhea
- Blood or mucus in the stool
- Belly pain that keeps coming back
- Weight loss or poor weight gain
- Fatigue or looking pale
- Fever without a clear cause
Some of these symptoms overlap with common, less serious childhood complaints. That overlap is exactly why the calprotectin test is useful. It helps clinicians decide which children need a closer look and which ones are likely dealing with something that will pass on its own.
When Should A Child Be Tested?
Calprotectin testing is most useful when a child has symptoms that could point to gut inflammation. It is not a routine screening test for healthy children with no symptoms.
Doctors commonly order it when a child has persistent diarrhea, blood in the stool, unexplained belly pain, poor growth, or a family history of IBD combined with digestive symptoms. It is also used to monitor children who already have a diagnosis of IBD.
The test is not a substitute for clinical judgment. A doctor weighs the result alongside the child’s history, physical exam, and other tests. If the picture is unclear, the next step may be imaging, blood tests, or, in some cases, a procedure such as an endoscopy or colonoscopy to look directly at the gut lining and take tissue samples.
What Happens After A High Result?
A high calprotectin level usually leads to more questions, not immediate answers. The first step is often to repeat the test, especially if the child recently had an infection. A value that drops back to normal points away from chronic disease.
If the level stays high, the doctor may order blood tests to look for signs of inflammation or anemia, stool tests to rule out infection, and imaging studies. In some cases, a referral to a pediatric gastroenterologist is made. That specialist may recommend an endoscopy or colonoscopy to examine the gut directly and confirm or rule out conditions like IBD.
Treatment depends entirely on the cause. An infection may need no treatment or a specific medication, depending on the organism. A food allergy is managed by removing the trigger food under medical guidance. IBD is managed with medications that reduce inflammation and keep it under control. There is no single treatment for a high calprotectin level, because the level itself is not the disease.
Does A High Level Always Mean Something Serious?
No. A high calprotectin level does not always mean a serious condition. Many children have a temporary rise from an infection or another short-lived cause, and the level returns to normal.
That said, a persistently high level should not be ignored. It is a signal that deserves follow-up. The goal of testing is to find the cause, whether it is minor and temporary or something that needs ongoing care. A result that stays elevated over time is more concerning than a single reading, and it is more likely to prompt further investigation.
The most useful thing a parent can do is make sure the result is interpreted by a clinician who has the full picture, and to follow through on recommended repeat testing or referrals. A number on a lab report is a starting point, not a finish line.
Frequently Asked Questions
Can a stomach bug cause high calprotectin in a child?
Yes, gastrointestinal infections are one of the most common causes of a temporarily high calprotectin level in children. Levels often return toward normal once the infection clears, which is why doctors sometimes repeat the test.
Does high calprotectin always mean IBD?
No, a high level does not always mean inflammatory bowel disease. Infections, food-protein allergies, celiac disease, and NSAID use can also raise calprotectin, so the result is interpreted alongside symptoms and other tests.
How long does it take for calprotectin to return to normal after an infection?
It varies by child and by the cause of the infection, and there is no single timeline that applies to everyone. Doctors often repeat the test after symptoms have resolved to see whether the level has fallen.
What calprotectin level is considered high in a child?
Reference ranges vary by laboratory, but levels above roughly 50 mcg/g are generally considered elevated, and levels above about 200 mcg/g are more likely to reflect active inflammation. Always check the reference range on your child’s specific lab report.
