Lf

Lactoferrin

Gastrointestinal

What is Lactoferrin?

Lactoferrin is an iron-binding glycoprotein found in high concentrations in neutrophil granules, breast milk, tears, saliva, and mucosal secretions. When intestinal inflammation occurs, activated neutrophils infiltrate the gut wall and release lactoferrin into the intestinal lumen, where it can be measured in stool samples as fecal lactoferrin. This protein is remarkably stable and resistant to proteolytic degradation, remaining detectable in stool samples for up to 5 days at room temperature, making it a reliable and practical biomarker.

Fecal lactoferrin serves a clinical role similar to fecal calprotectin as a non-invasive marker of intestinal inflammation. It is particularly useful for distinguishing inflammatory bowel disease (IBD) from functional gastrointestinal disorders like irritable bowel syndrome (IBS). Beyond its role as an inflammatory marker, lactoferrin has intrinsic antimicrobial properties—it sequesters iron from pathogenic bacteria (iron is essential for bacterial growth), directly damages bacterial cell membranes, and modulates the immune response. Lactoferrin is also a major component of breast milk, providing innate immune protection to newborns.

Why It Matters

Fecal lactoferrin is a highly sensitive and specific marker for neutrophilic intestinal inflammation. Its clinical significance parallels fecal calprotectin—it effectively distinguishes IBD from IBS, reducing unnecessary colonoscopies, and serves as a monitoring tool for disease activity in established IBD. Lactoferrin levels correlate with endoscopic and histological disease severity in both Crohn's disease and ulcerative colitis. The test is particularly valuable in clinical settings where calprotectin testing is unavailable, and some studies suggest lactoferrin may be more specific than calprotectin in certain clinical scenarios. As a natural antimicrobial protein, lactoferrin also reflects the gut's innate immune defense status.

Normal Reference Ranges

GroupRangeUnit
Adults (negative)<7.25mcg/g
Positive (inflammation likely)≥7.25mcg/g

Reference ranges may vary by laboratory. Always compare results to the ranges provided by your testing facility.

What High Lf Levels Mean

Common Causes

  • Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
  • Bacterial gastroenteritis (Salmonella, Shigella, Campylobacter)
  • Clostridioides difficile infection
  • Colorectal cancer
  • NSAID-induced enteropathy
  • Diverticulitis
  • Necrotizing enterocolitis (in neonates)

Possible Symptoms

  • Diarrhea (often bloody or mucus-containing)
  • Abdominal pain and cramping
  • Fever
  • Urgency and tenesmus
  • Weight loss and fatigue
  • Rectal bleeding

What to do: Elevated fecal lactoferrin indicates significant intestinal inflammation and warrants further workup. Colonoscopy with biopsies is typically indicated to determine the cause. Rule out infectious etiologies with stool cultures and C. difficile testing. For known IBD patients, elevated lactoferrin during remission may signal subclinical inflammation or impending relapse, warranting treatment review with your gastroenterologist. Discontinue NSAIDs if applicable and retest.

What Low Lf Levels Mean

Common Causes

  • Normal finding—indicates no significant neutrophilic intestinal inflammation
  • Irritable bowel syndrome (lactoferrin is typically normal)
  • Functional dyspepsia
  • IBD in complete mucosal remission

Possible Symptoms

  • No symptoms—negative fecal lactoferrin is the expected healthy result

What to do: A negative fecal lactoferrin result is reassuring and strongly argues against active inflammatory bowel disease. If gastrointestinal symptoms persist, consider evaluation for functional GI disorders, food sensitivities, celiac disease, or small intestinal bacterial overgrowth. For IBD patients in remission, a negative lactoferrin supports mucosal healing and adequacy of current therapy.

When Is Lf Testing Recommended?

  • To differentiate IBD from IBS in patients with chronic GI symptoms
  • When evaluating chronic diarrhea of unknown cause
  • To monitor disease activity in established IBD
  • To assess mucosal healing after IBD treatment changes
  • When infectious colitis is suspected
  • As an alternative to fecal calprotectin when unavailable

Frequently Asked Questions

Both are neutrophil-derived proteins used to detect intestinal inflammation, and their clinical utility is very similar. Calprotectin is more widely studied and used globally, with more established reference ranges and cutoff values. Lactoferrin may have slightly higher specificity for IBD in some studies and is more stable at room temperature. In practice, either test can be used to distinguish IBD from IBS, monitor disease activity, and predict relapse. The choice often depends on local laboratory availability and physician preference.
The protein itself is the same, but the source and clinical context differ entirely. Breast milk contains very high concentrations of lactoferrin (approximately 1–2 g/L in mature milk, even higher in colostrum) produced by mammary gland epithelial cells. This lactoferrin provides antimicrobial and immune protection to the nursing infant. Fecal lactoferrin, measured clinically, comes from neutrophils that have migrated into the inflamed intestinal wall. In breastfed infants, some breast milk lactoferrin may appear in stool, which should be considered when interpreting fecal lactoferrin results in this population.
Yes, NSAIDs (ibuprofen, naproxen, aspirin) can cause intestinal mucosal inflammation and neutrophil infiltration, leading to elevated fecal lactoferrin even in the absence of IBD. Patients should ideally stop NSAIDs for 2 weeks before testing. Proton pump inhibitors (PPIs) may also mildly elevate levels. Immunosuppressive medications used to treat IBD (such as azathioprine, methotrexate, or biologics like infliximab) typically reduce fecal lactoferrin by controlling intestinal inflammation—this is the desired therapeutic effect and a sign of treatment success.

Related Biomarkers

fCalCalprotectinALBAlbumin

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Medical Disclaimer: This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Reference ranges may vary between laboratories. Always consult your healthcare provider for interpretation of your specific test results.

Disclaimer: SymptomGPT is not a medical diagnosis tool and does not provide medical advice. Always consult a qualified healthcare professional. If you are experiencing a medical emergency, call 911 immediately.