Fecal calprotectin is a stool test that helps measure inflammation in the digestive tract, especially the intestines. In many laboratories, a result below 50 micrograms per gram (µg/g) is considered normal, but the exact reference range can vary. A higher result does not diagnose a specific disease on its own; it usually suggests that inflammation may be present and that conditions such as inflammatory bowel disease should be considered, while a low result makes significant intestinal inflammation less likely. According to the NHS and major gastroenterology guidelines, this test is mainly used to help distinguish inflammatory causes of symptoms from non-inflammatory causes such as irritable bowel syndrome.
What fecal calprotectin measures
Calprotectin is a protein found in certain white blood cells called neutrophils. When the lining of the intestines becomes inflamed, these cells move into the bowel wall and release calprotectin into the stool. The test measures how much of this protein is present in a sample of stool.
In simple terms, the test acts like a signal of gut inflammation. It does not tell you exactly why the inflammation is happening, but it can help a clinician decide whether further testing is needed. The British Society of Gastroenterology and NHS guidance describe it as a useful tool for evaluating people with ongoing bowel symptoms, especially when doctors want to avoid unnecessary colonoscopy in lower-risk situations.
When the test is used
Doctors often order fecal calprotectin when a person has symptoms such as:
- ongoing diarrhea
- belly pain or cramping
- bloating
- weight loss
- rectal bleeding
- mucus in the stool
- repeated urgent bowel movements
The test is particularly helpful when a clinician is trying to tell the difference between inflammatory bowel disease, such as Crohn’s disease or ulcerative colitis, and functional disorders such as irritable bowel syndrome. According to the NIH and gastroenterology societies, this distinction matters because the treatment approach is very different.
Doctors may also use the test to help monitor known inflammatory bowel disease. In that setting, changes in fecal calprotectin can sometimes reflect changes in intestinal inflammation before symptoms become obvious.
Fecal calprotectin normal range and reference values
A common reference range for adults is:
- less than 50 µg/g: usually considered normal
- 50 to 100 µg/g: often considered borderline or mildly elevated
- above 100 µg/g: more likely to suggest intestinal inflammation
- above 250 µg/g: often associated with more active inflammation in many clinical settings
These cutoffs are not universal. According to the NHS and laboratory guidance, reference ranges may differ between laboratories, and some labs use different decision points. Age also matters. Infants and young children can have higher values than adults, especially in early life, so pediatric interpretation should always use the laboratory’s age-specific reference range.
A single result should never be interpreted in isolation. Doctors consider symptoms, medications, recent infections, and other test results before drawing conclusions.
What a high fecal calprotectin result may mean
A high fecal calprotectin result usually suggests inflammation somewhere in the intestines, but it does not identify the exact cause. Common possibilities include:
- Crohn’s disease
- ulcerative colitis
- infectious gastroenteritis (a stomach or intestinal infection)
- diverticulitis
- colorectal cancer in some cases
- use of certain medicines
- other inflammatory bowel conditions
The Mayo Clinic and NHS note that non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and naproxen, can sometimes raise fecal calprotectin. Recent bowel infections can also increase the level for a period of time. This is one reason clinicians often repeat the test or combine it with other assessments if the result is unexpected.
A mildly raised result does not always mean a serious disease is present. In some people, a repeat test may fall back into the normal range, especially if the trigger was temporary.
What a low fecal calprotectin result may mean
A low result generally makes significant inflammation in the intestines less likely. In practice, this can support the idea that symptoms may be due to irritable bowel syndrome or another non-inflammatory cause, especially if the rest of the medical evaluation fits that picture.
That said, no test is perfect. Some people with early or mild inflammatory bowel disease can still have lower readings, and results can change over time. If symptoms are persistent, severe, or changing, a doctor may still recommend additional testing even when calprotectin is normal.
How the fecal calprotectin test is done
The test uses a small stool sample. In most cases, you collect the sample at home using a container provided by the clinic or laboratory. You then return it for analysis.
The process is usually straightforward:
- Collect a small stool sample in the approved container.
- Avoid contaminating the sample with urine or toilet water.
- Return the sample promptly, following the lab’s instructions.
- Wait for the result, which may take a few days depending on the facility.
Some laboratories provide special instructions about diet, medications, or timing, but many people do not need to fast before the test. If you take NSAIDs or other medicines that may affect the result, your clinician may advise whether to pause them before testing.
Factors that can affect the result
Several things can influence fecal calprotectin:
- recent intestinal infection
- NSAID use
- gastrointestinal bleeding in some cases
- active inflammatory bowel disease
- sample handling issues
- age, especially in infants and young children
Because of these factors, doctors often look at the full clinical picture rather than using the number alone. If a result is borderline, a repeat test after a short interval may help clarify whether inflammation is ongoing.
Fecal calprotectin and inflammatory bowel disease
Inflammatory bowel disease, or IBD, includes Crohn’s disease and ulcerative colitis. These conditions cause ongoing inflammation in the digestive tract. According to the NHS and major gastroenterology guidance, fecal calprotectin is useful because it tends to be higher when IBD is active.
In people already diagnosed with IBD, the test can sometimes help monitor disease activity. For example, if symptoms improve and calprotectin falls, that may suggest the inflammation is also improving. However, a doctor may still use blood tests, imaging, or colonoscopy depending on the situation.
The test does not replace endoscopy when a direct look at the bowel is needed. Instead, it often helps decide who is more likely to benefit from further investigation.
Fecal calprotectin and irritable bowel syndrome
Irritable bowel syndrome, or IBS, causes symptoms such as abdominal pain, bloating, constipation, diarrhea, or a mix of bowel changes. IBS does not usually cause intestinal inflammation. For that reason, fecal calprotectin is often normal in IBS.
This makes the test useful when symptoms overlap. If a person has bowel complaints and calprotectin is low, a clinician may be more confident that an inflammatory disease is less likely. If the result is elevated, the doctor may look more closely for IBD or another inflammatory cause.
Still, IBS can only be diagnosed after a proper medical assessment. A normal calprotectin result does not confirm IBS by itself.
What happens after the result
Next steps depend on the number, your symptoms, and your medical history.
If the result is normal, a doctor may reassure you, treat symptoms, or investigate other causes if needed.
If the result is mildly elevated, your doctor may:
- repeat the test
- review medicines such as NSAIDs
- check for recent infection
- order blood tests
- refer you to a gastroenterologist
If the result is clearly elevated, especially with warning symptoms such as weight loss, blood in the stool, fever, anemia, or persistent diarrhea, your doctor may recommend colonoscopy or another specialist assessment. According to the British Society of Gastroenterology, the decision depends on the whole clinical picture, not the test alone.
Limitations of fecal calprotectin
Fecal calprotectin is helpful, but it has limits. It can show that inflammation may be present, yet it cannot tell the exact cause or location. It also cannot reliably rule out every bowel disorder.
In addition, some cancers, infections, and medication effects can raise the result, which means a high reading is not specific to IBD. On the other hand, a normal result does not completely exclude every serious condition. This is why clinicians use the test as one piece of a larger evaluation.
How doctors interpret borderline results
Borderline results are common and often need context. A value between 50 and 100 µg/g may be interpreted differently depending on the lab, age, symptoms, and whether the person has taken NSAIDs or recently had an infection.
In many cases, doctors repeat the test after a short time rather than rushing to invasive testing. If the value rises or symptoms worsen, they may investigate further. If it falls, that may suggest the inflammation was temporary.
When to see a doctor
See a doctor promptly if you have ongoing bowel symptoms and any of the following:
- blood in the stool
- black or tarry stool
- unexplained weight loss
- fever with diarrhea
- severe or worsening belly pain
- dehydration
- anemia or extreme tiredness
- waking from sleep to pass stool
- a fecal calprotectin result above the lab’s upper limit, especially if it is above 100 µg/g and symptoms persist
- a markedly high result, such as above 250 µg/g, if your clinician has not already explained the cause
Seek urgent medical care if you have severe abdominal pain, signs of dehydration, fainting, persistent vomiting, or heavy rectal bleeding.
Frequently asked questions
Is fecal calprotectin the same as a blood test?
No. Fecal calprotectin is measured in stool, not blood. It reflects inflammation in the intestines more directly than many blood tests do.
Does a high result always mean inflammatory bowel disease?
No. A high result suggests inflammation, but the cause may be infection, medication use, diverticulitis, or another condition. A doctor needs to interpret the result in context.
Can stress raise fecal calprotectin?
Stress may worsen bowel symptoms, but it does not usually cause a major rise in fecal calprotectin by itself. If the level is elevated, clinicians usually look for inflammation or another medical cause.
Should I stop ibuprofen before the test?
Possibly, but only if your doctor or lab advises it. NSAIDs such as ibuprofen can sometimes raise fecal calprotectin, so clinicians may ask you to pause them before testing.
How long does it take to get results?
This depends on the laboratory. Many results are available within a few days, but turnaround times can vary.
Can children have different normal values?
Yes. Children, especially infants, can have different reference ranges from adults. Always use the age-specific range provided by the laboratory and your child’s clinician.
Glossary of key terms
- Calprotectin: A protein released by certain white blood cells during inflammation.
- Neutrophils: White blood cells that help fight infection and are often present in inflamed tissue.
- Inflammation: The body’s response to injury or irritation, which can cause swelling, pain, and tissue changes.
- Inflammatory bowel disease (IBD): A group of long-term conditions that cause inflammation in the digestive tract, mainly Crohn’s disease and ulcerative colitis.
- Irritable bowel syndrome (IBS): A common bowel disorder that causes pain and changes in bowel habits without visible inflammation.
- Colonoscopy: A procedure that lets a doctor look inside the colon using a flexible camera.
- NSAIDs: Non-steroidal anti-inflammatory drugs, such as ibuprofen and naproxen.
Sources
- Cleveland Clinic – Fecal Calprotectin Test
- Mayo Clinic Laboratories – Calprotectin, Feces (Test Overview)
- NIH/PMC – Guidance on the interpretation of faecal calprotectin levels in children
Further reading
Understand your lab results with AI DiagMe
Understanding fecal calprotectin is one part of making sense of your health, but lab results are most useful when they are interpreted in the context of your symptoms, medicines, and medical history. AI DiagMe can help you better understand what your test results may mean and what questions to ask your clinician next.
➡️ Get your results interpreted in minutes
