Lab result explainedInflammationLast updated November 11, 2026

Fecal lactoferrin test: what a positive result means, normal values, and lactoferrin versus calprotectin

Fecal lactoferrin · Fecal lactoferrin (stool sample), qualitative or quantitative; often ordered with stool culture, C. difficile testing, fecal calprotectin, CBC and CRP · reported in Qualitative: negative or positive. Quantitative: µg/g of stool (the same as mg/kg)

Fecal lactoferrin is a protein that neutrophils (the main white cells of acute inflammation) carry in their granules and release when they move into the bowel wall, so finding it in a stool sample is a sign that the intestine is inflamed. The test is reported either as negative or positive (the common US format) or as a number, with normal usually under about 7.25 µg/g of stool. A positive result means neutrophils are entering the gut, which happens in inflammatory bowel disease (Crohn's disease and ulcerative colitis) and in bacterial infections of the bowel, and does not happen in irritable bowel syndrome.

It is used for two main purposes. In someone with chronic diarrhea or abdominal pain, it helps decide whether the symptoms come from inflammation (which needs stool cultures and often colonoscopy) or from a functional disorder such as IBS; a meta-analysis of studies comparing IBD with IBS found a pooled sensitivity of about 80 percent and specificity of about 80 to 85 percent. In someone with acute diarrhea, it flags an inflammatory, usually bacterial, cause such as Salmonella, Shigella, Campylobacter or Clostridioides difficile, which changes how the illness is investigated.

Lactoferrin does the same job as fecal calprotectin, and the two markers track each other closely, but calprotectin has been studied more widely, has better-defined numerical cut-offs for monitoring IBD, and is the test most guidelines name. Lactoferrin remains in use in many US laboratories, is cheaper in its qualitative form, and has one specific pitfall: because breast milk is rich in lactoferrin, the test is unreliable in breastfed infants. Like calprotectin, it can also be turned positive by NSAIDs and by bleeding.

Fecal lactoferrin at a glance

  • What it is: an iron-binding protein from neutrophil granules measured in stool; it reflects white-cell traffic into the bowel wall.
  • Normal: negative on the qualitative test, or under about 7.25 µg/g on the quantitative ELISA (labs differ; some report mg/kg, which is the same number).
  • Positive or raised: neutrophilic inflammation, most often active Crohn's disease, ulcerative colitis or bacterial gastroenteritis; also NSAID damage, diverticulitis, bleeding and some cancers.
  • Negative in IBS and in most viral gastroenteritis; a negative result in an adult with typical IBS symptoms makes IBD unlikely but is less reassuring than a normal calprotectin.
  • Not valid in breastfed infants (breast milk lactoferrin) and less reliable in the first year of life generally.
  • Next step for a positive result: stool culture or PCR panel and C. difficile testing if diarrhea is acute; CBC, CRP, ferritin, calprotectin and colonoscopy if symptoms are chronic.

Have your whole report? Paste it into the free Lab Explainer

Every marker explained in plain language, in context with the others, with questions to bring to your appointment. No account needed.

What Fecal lactoferrin measures

Lactoferrin is a glycoprotein that binds iron and is found in the secondary granules of neutrophils and in body fluids such as breast milk, tears and saliva, where it helps restrict bacterial growth. Normal stool contains very little. When the bowel lining is inflamed, neutrophils cross into the lumen, degranulate and die, releasing lactoferrin, which is resistant to digestion and stable in stool for several days at room temperature and longer refrigerated. The amount recovered from a sample therefore reflects how many neutrophils have passed into the gut over roughly the previous day, in the same way as calprotectin.

Two formats exist. The qualitative latex agglutination or lateral-flow test gives a positive or negative result at a fixed threshold and takes minutes; it was developed as a cleaner substitute for the old fecal leukocyte smear, which depends on fresh samples and a skilled microscopist. The quantitative ELISA reports a concentration in micrograms of lactoferrin per gram of stool, with a commonly used upper limit of normal of 7.25 µg/g, and is the format used in IBD monitoring studies. Both use antibodies specific to human lactoferrin, so dietary animal lactoferrin (in dairy, for instance) does not normally interfere.

A pea-sized sample from a single stool is enough. Diet and fasting do not matter, but recent NSAIDs, a colonoscopy preparation, menstrual blood and significant gastrointestinal bleeding all push the result upward. In breastfed infants, swallowed milk lactoferrin passes through to the stool and gives positive results in healthy babies, so the test is not interpretable before weaning and is used cautiously in the first year of life.

Normal range for Fecal lactoferrin

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (Qualitative: negative or positive. Quantitative: µg/g of stool (the same as mg/kg))Notes
Negative (qualitative test)No lactoferrin detected above the assay thresholdExpected in healthy people, IBS, most viral gastroenteritis and IBD in deep remission.
Positive (qualitative test)Lactoferrin detectedNeutrophilic inflammation present; cause not specified. Repeat off NSAIDs if the picture does not fit.
Quantitative, normalBelow about 7.25 µg/gThe cut-off used by the most widely studied ELISA; labs differ, so use the printed limit.
Quantitative, mildly raisedAbout 7.25–30 µg/gLow-grade inflammation or interference: NSAIDs, mild infection, bleeding, diverticular disease, or IBD in partial remission.
Quantitative, clearly raisedAbove about 30–50 µg/gActive IBD or bacterial colitis likely; values in the hundreds occur in active ulcerative colitis and severe infection.
Known IBD, remissionNegative, or below about 7.25 µg/gCorrelates with a healed lining; a return to positive or a rising value predicts relapse.
Breastfed infantsFrequently positive in healthNot interpretable; breast milk is rich in lactoferrin. Use age-appropriate tests or calprotectin with pediatric cut-offs.

Positive or raised fecal lactoferrin

A positive lactoferrin means neutrophils are entering your bowel: there is active inflammation somewhere in the intestine. The test does not say where or why. In someone with acute diarrhea (less than two weeks), a positive result shifts the likely cause from a virus to an invasive bacterium such as Salmonella, Shigella, Campylobacter, enteroinvasive or Shiga-toxin E. coli, or C. difficile, and most clinicians will then send stool for culture or a PCR panel and C. difficile testing. In studies of acute diarrhea, lactoferrin positivity has a sensitivity of about 90 percent for bacterial colitis but a specificity of only about 70 percent, so a negative result is more useful for excluding bacterial infection than a positive one is for confirming it.

In someone with chronic symptoms (more than four weeks of diarrhea, pain, urgency, blood or weight loss), a positive lactoferrin raises the probability of inflammatory bowel disease substantially and usually leads to colonoscopy with biopsies. Across studies comparing IBD with IBS and healthy controls, lactoferrin has a sensitivity of roughly 80 percent and specificity of 80 to 85 percent, slightly below calprotectin on both counts. The positive predictive value depends on the setting: in a gastroenterology clinic where IBD is common, most positives are IBD; in primary care, a fair share will be infections, NSAID effects or bleeding. A positive test in someone over 50 with a change in bowel habit, or with anemia, needs colonoscopy regardless, because colorectal cancer and large polyps can also attract neutrophils.

In someone who already has IBD, a positive or rising lactoferrin indicates active mucosal inflammation even when symptoms are mild, and in monitoring studies it predicted relapse over the following months with about 60 to 80 percent accuracy. For detecting endoscopically active disease in symptomatic patients, a meta-analysis found lactoferrin had a pooled sensitivity of 82 percent and specificity of 79 percent, compared with 88 and 73 percent for calprotectin and 49 and 92 percent for CRP. A negative lactoferrin in known IBD is good evidence that the lining has healed, though small-bowel Crohn's disease can be active with little lactoferrin reaching the stool.

Common causes

  1. Ulcerative colitis

    Produces the strongest positives because the inflamed surface is large and in continuity with the stool stream; quantitative values in active extensive colitis often run into the hundreds of µg/g and fall to negative with mucosal healing.

  2. Crohn's disease

    Positive in most people with active colonic or ileocolonic disease; disease limited to the small bowel or upper gut can give lower values or a negative result, so a negative test does not exclude Crohn's disease when suspicion is high.

  3. Bacterial gastroenteritis and C. difficile infection

    Salmonella, Shigella, Campylobacter, Yersinia, invasive and Shiga-toxin E. coli and C. difficile all cause neutrophilic colitis with a positive lactoferrin that typically clears within 2 to 4 weeks of recovery. Viral causes (norovirus, rotavirus) are usually negative, and toxin-mediated food poisoning (Staph aureus, Bacillus cereus) is negative.

  4. NSAIDs and aspirin

    Regular ibuprofen, naproxen, diclofenac or aspirin injure the gut lining and can turn the test positive in people with no bowel disease, in the same way as they raise calprotectin. Stop for 2 to 4 weeks before a repeat sample unless the drug is essential.

  5. Gastrointestinal bleeding and menstrual contamination

    Blood contains neutrophils, so a bleeding ulcer, hemorrhoids, a vascular malformation or menstrual blood in the sample can all cause a positive, usually mild, result.

  6. Diverticulitis and ischemic colitis

    Acute diverticulitis and reduced blood flow to the colon both cause neutrophilic inflammation and positive results; symptomatic diverticular disease can give persistent low-level positives in older adults.

  7. Colorectal cancer and large polyps

    Tumors attract neutrophils and bleed; lactoferrin is positive in a proportion of cancers but is not a screening test for them, and a persistently positive result in someone over 50 is one more reason for colonoscopy.

  8. Parasitic infection

    Entamoeba histolytica (amoebic colitis) gives a positive result; Giardia and most other parasites cause little neutrophil response and are usually negative, so a negative test does not exclude them.

  9. Breastfeeding and infancy

    Human milk contains large amounts of lactoferrin that pass through the infant gut, so breastfed babies test positive in health. The test should not be used before weaning and is interpreted cautiously in the first year.

  10. Recent colonoscopy preparation or biopsy, and radiation enteritis

    Bowel preparation and mucosal biopsies transiently increase neutrophil shedding; collect the sample before the procedure. Pelvic radiation produces a chronic neutrophilic proctitis with persistent positives.

Symptoms that can go with it

  • Acute diarrhea with fever, cramping and blood or mucus (dysentery pattern) in bacterial infection
  • Diarrhea lasting more than 4 weeks, urgency, or being woken at night by the need to pass stool
  • Blood or mucus in the stool
  • Abdominal pain, often right lower abdomen in Crohn's disease or left-sided and crampy in colitis
  • Unintentional weight loss, or poor growth in children
  • Fatigue and breathlessness from iron-deficiency anemia
  • Sometimes no symptoms at all in monitored IBD, where a positive test precedes a flare

Read it alongside

  • Fecal calprotectin — the more extensively validated neutrophil marker with numeric targets for IBD; the two agree in most cases and some labs run both.
  • Stool culture, multiplex PCR panel and C. difficile toxin or PCR — identify the organism when lactoferrin is positive in acute diarrhea.
  • CRP — raised in only about half of people with active IBD; a positive lactoferrin with a normal CRP is common and still meaningful.
  • Complete blood count — anemia, a high platelet count or a high white count support significant inflammation.
  • Ferritin and iron saturation — iron deficiency alongside a positive lactoferrin points to organic bowel disease rather than IBS.
  • Albumin — falls with severe or prolonged intestinal inflammation.
  • FIT test — detects hidden blood and is the appropriate colorectal cancer screening test; lactoferrin is not.
  • tTG-IgA — celiac disease produces little neutrophilic inflammation, so it is tested for separately in chronic diarrhea.

What usually happens next

  1. If you have acute diarrhea and the test is positive, expect stool culture or a PCR panel and C. difficile testing; results guide whether an antibiotic is appropriate (many bacterial diarrheas do not need one) and whether public health needs notifying.
  2. If you have chronic symptoms and the test is positive, expect CBC, CRP, ferritin and often a calprotectin, followed by colonoscopy with biopsies; if the colon is normal and Crohn's disease is still suspected, small-bowel imaging or capsule endoscopy follows.
  3. If the test is positive but your symptoms are mild and you have been taking NSAIDs or aspirin, ask whether to stop them (if safe) and repeat in 2 to 4 weeks before proceeding to colonoscopy.
  4. If the test is negative and your symptoms fit IBS with no red flags (no bleeding, weight loss, anemia, nocturnal symptoms, family history, age over 50), IBD is unlikely; a calprotectin is sometimes added for extra reassurance because it is slightly more sensitive.
  5. If you have known IBD and your lactoferrin has turned positive or risen, expect an earlier review of treatment rather than waiting for symptoms; ask whether your clinic prefers calprotectin for monitoring, since numeric targets are better defined for it.
  6. Collect the sample from a single stool into the container provided, avoiding toilet water, urine, menstrual blood and the days after a colonoscopy preparation; return it within the lab's time window (several days at room temperature, longer refrigerated).

Diet, lifestyle and natural levers with evidence

What can move Fecal lactoferrin once the cause is known. Nothing here replaces finding the cause.

Stop NSAIDs for 2 to 4 weeks before testing, and avoid sampling during bleeding or menstruation

Strong evidence

NSAID enteropathy is a well-documented cause of neutrophil shedding into the gut: in volunteer and patient studies using calprotectin (the sister marker), two weeks of regular NSAIDs raised the result above normal in around half of people, and lactoferrin behaves the same way. Acetaminophen does not affect the test. Menstrual blood or a hemorrhoidal bleed in the sample can also turn it positive, so time the collection to avoid them. Nothing dietary changes the result in a healthy person; the test measures inflammation, not what you ate.

Do not stop prescribed low-dose aspirin after a stent, heart attack or stroke without asking the prescriber.

Stopping smoking in Crohn's disease

Strong evidence

Smoking roughly doubles the risk of Crohn's disease and worsens its course. In a prospective study of 474 smokers with Crohn's disease, those who quit for more than a year had about 65 percent fewer flares than continuing smokers and needed fewer steroids and immunosuppressants. Lower disease activity means less neutrophil traffic and a negative or lower lactoferrin.

Mediterranean-style diet and fiber in IBD

Moderate evidence

In the 194-patient DINE-CD trial, a Mediterranean diet performed as well as the specific carbohydrate diet for symptomatic remission in mild to moderate Crohn's disease (about 44 versus 47 percent at 12 weeks) and was easier to follow, with a minority in each group achieving normalization of fecal inflammatory markers. A 6-month study of 142 IBD patients linked Mediterranean diet adherence with lower calprotectin, CRP and disease activity. Cohort studies associate higher fiber and lower ultra-processed food intake with fewer flares.

Increase fiber cautiously during a stricturing Crohn's flare, and discuss major dietary changes with your IBD team or dietitian.

Curcumin as add-on therapy in ulcerative colitis

Moderate evidence

Adding 3 g a day of curcumin to mesalamine for 4 weeks in 50 people with mild to moderate ulcerative colitis not responding to mesalamine alone produced clinical remission in 54 percent versus none on placebo, with endoscopic improvement in 38 percent versus none; a 6-month maintenance trial of 2 g a day cut relapse from about 21 to 5 percent. Fewer neutrophils in a healing lining translates into a falling stool marker, although lactoferrin itself was not the measured outcome.

May increase bleeding with anticoagulants, provoke gallbladder pain in people with gallstones and rarely injure the liver at high doses; it supplements prescribed treatment rather than replacing it.

Multi-strain probiotics in ulcerative colitis

Moderate evidence

A high-dose eight-strain probiotic added to standard therapy induced remission in about 43 percent versus 16 percent on placebo in a 144-patient trial of mild to moderate ulcerative colitis, and E. coli Nissle 1917 maintained remission as effectively as mesalamine in several trials. Evidence in Crohn's disease is largely negative, and in acute infectious diarrhea probiotics shorten illness by about a day in children but do not alter the inflammatory marker.

Avoid in severely immunocompromised people and those with central venous catheters without medical advice, because of rare bloodstream infections.

When to see a clinician promptly

  • Six or more bloody stools a day with fever, a heart rate over 90, or feeling faint: possible acute severe colitis or severe bacterial infection, needing same-day assessment.
  • Severe abdominal pain with a swollen, tense abdomen or persistent vomiting, which can indicate toxic megacolon, obstruction or perforation.
  • Signs of dehydration with diarrhea (dizziness on standing, very little urine, confusion), especially in older adults, young children and anyone on diuretics or immunosuppressants.
  • Bloody diarrhea within a few weeks of antibiotics or a hospital stay, which raises the possibility of C. difficile infection.
  • A positive lactoferrin with weight loss, anemia, a persistent change in bowel habit, or age over 50, which needs colonoscopy rather than a repeat stool test.
  • In known IBD, a newly positive or rising lactoferrin even without symptoms, to adjust treatment before a flare.

Frequently asked questions

What does a positive fecal lactoferrin mean?

It means neutrophils, the white cells of acute inflammation, are moving into your bowel wall and being shed into the stool, so some part of your intestine is inflamed. With acute diarrhea it points to a bacterial cause such as Salmonella, Campylobacter, Shigella or C. difficile; with chronic symptoms it raises the likelihood of Crohn's disease or ulcerative colitis. NSAIDs, bleeding, diverticulitis and bowel polyps or cancer can also cause a positive result, so the next step is usually stool infection tests and, for chronic symptoms, colonoscopy.

Lactoferrin versus calprotectin: which test is better?

They measure the same thing, neutrophil traffic into the gut, and agree in most patients. Calprotectin has been studied far more, has better-established numeric cut-offs (under 50 µg/g normal; under 150 to 250 µg/g for mucosal healing in IBD), is slightly more sensitive for IBD (around 93 percent versus 80 percent in adult meta-analyses), and is the marker named in most guidelines. Lactoferrin is cheaper in its qualitative form and useful for triaging acute diarrhea, but is unreliable in breastfed infants. If you have a choice for IBD diagnosis or monitoring, calprotectin is generally preferred; if your lab runs lactoferrin, a negative result is still reasonably reassuring.

What is a normal lactoferrin level in stool?

On the qualitative test, negative. On the quantitative ELISA, under about 7.25 µg/g (equivalent to 7.25 mg/kg) is the most widely used upper limit of normal, but laboratories use different assays and thresholds, so go by the range on your report. Values up to about 30 µg/g are mildly raised and often reflect NSAIDs, mild infection or bleeding; values above 30 to 50 µg/g suggest active IBD or bacterial colitis.

Can a stomach bug cause a positive lactoferrin?

Yes. Invasive bacterial infections (Salmonella, Shigella, Campylobacter, Yersinia, some E. coli strains, C. difficile) and amoebic dysentery all produce neutrophilic inflammation and a positive test, which usually turns negative within 2 to 4 weeks of recovery. Most viral gastroenteritis (norovirus, rotavirus) and toxin-type food poisoning do not. If a positive result was taken during or shortly after a diarrheal illness, it is repeated once you have been well for a month before IBD is considered.

Is fecal lactoferrin positive in IBS?

No. Irritable bowel syndrome does not inflame the bowel lining, so lactoferrin should be negative. That is the basis of its use: in people with chronic bowel symptoms, a negative result supports IBS and a positive result points away from it toward IBD or another inflammatory cause. Because lactoferrin misses about 20 percent of IBD, a negative test is not absolute, and red-flag features (bleeding, weight loss, anemia, nocturnal symptoms, family history, age over 50) still warrant colonoscopy.

Why is the test unreliable in breastfed babies?

Human breast milk contains high concentrations of lactoferrin, which survives passage through the infant gut and appears in the stool, so healthy breastfed babies routinely test positive. The assay cannot tell milk lactoferrin from neutrophil lactoferrin. Formula-fed infants are less affected, but levels of both lactoferrin and calprotectin are naturally higher throughout the first year, so pediatricians rely on age-specific calprotectin cut-offs or other tests in infants.

What if lactoferrin is positive but my colonoscopy was normal?

The commonest explanations are an infection or NSAID effect that had resolved by the time of the scope, a bleed, or Crohn's disease in the small bowel beyond the colonoscope's reach. If symptoms persist, your clinician may repeat the stool marker, review medications, and image the small bowel with MR enterography or capsule endoscopy. Microscopic colitis is diagnosed on biopsies from a normal-looking colon, though it usually leaves lactoferrin negative or only slightly raised.

Does taking a lactoferrin supplement affect the stool test?

It is unlikely but not impossible. Supplements contain bovine (cow) lactoferrin, and the clinical assays use antibodies raised against human lactoferrin, which largely do not cross-react; dairy intake does not interfere. There are no published studies of high-dose supplements and the stool test, so if you take one, mention it, and if a positive result is unexpected, consider pausing it for a week before a repeat.

References

  1. Gisbert JP, McNicholl AG, Gomollon F. Questions and answers on the role of fecal lactoferrin as a biological marker in inflammatory bowel disease. Inflammatory Bowel Diseases (2009)
  2. Kane SV, Sandborn WJ, Rufo PA, et al.. Fecal lactoferrin is a sensitive and specific marker in identifying intestinal inflammation. American Journal of Gastroenterology (2003)
  3. Mosli MH, Zou G, Garg SK, et al.. C-reactive protein, fecal calprotectin, and stool lactoferrin for detection of endoscopic activity in symptomatic inflammatory bowel disease patients: a systematic review and meta-analysis. American Journal of Gastroenterology (2015)
  4. Guerrant RL, Araujo V, Soares E, et al.. Measurement of fecal lactoferrin as a marker of fecal leukocytes. Journal of Clinical Microbiology (1992)
  5. Shane AL, Mody RK, Crump JA, et al.. 2017 Infectious Diseases Society of America clinical practice guidelines for the diagnosis and management of infectious diarrhea. Clinical Infectious Diseases (2017)
  6. Riddle MS, DuPont HL, Connor BA. ACG clinical guideline: diagnosis, treatment, and prevention of acute diarrheal infections in adults. American Journal of Gastroenterology (2016)
  7. Langhorst J, Elsenbruch S, Koelzer J, Rueffer A, Michalsen A, Dobos GJ. Noninvasive markers in the assessment of intestinal inflammation in inflammatory bowel diseases: performance of fecal lactoferrin, calprotectin, and PMN-elastase, CRP, and clinical indices. American Journal of Gastroenterology (2008)
  8. Schoepfer AM, Trummler M, Seeholzer P, Seibold-Schmid B, Seibold F. Discriminating IBD from IBS: comparison of the test performance of fecal markers, blood leukocytes, CRP, and IBD antibodies. Inflammatory Bowel Diseases (2008)
  9. Walker TR, Land ML, Kartashov A, et al.. Fecal lactoferrin is a sensitive and specific marker of disease activity in children and young adults with inflammatory bowel disease. Journal of Pediatric Gastroenterology and Nutrition (2007)
  10. van Rheenen PF, Van de Vijver E, Fidler V. Faecal calprotectin for screening of patients with suspected inflammatory bowel disease: diagnostic meta-analysis. BMJ (2010)
  11. Cosnes J, Beaugerie L, Carbonnel F, Gendre JP. Smoking cessation and the course of Crohn's disease: an intervention study. Gastroenterology (2001)
  12. Overview of gastroenteritis. Merck Manual Professional Version (2024)

Related markers

Related conditions

Evidence guides

Worried about your number?

Ask AskMN what your Fecal lactoferrin result could mean in the context of your other results, symptoms and medications. Free, unlimited, no account needed.

Ask about my Fecal lactoferrin

This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.