What does the Faecal Calprotectin test measure?

Why is Faecal Calprotectin measured?

Faecal calprotectin is the single most useful stool biomarker for distinguishing organic inflammatory bowel disease from functional gastrointestinal disorders. Elevated levels indicate active intestinal inflammation — most commonly Crohn's disease or ulcerative colitis — and support prioritisation for endoscopy, whereas normal or low values make IBD unlikely and reduce the need for invasive investigation. In patients with established IBD, serial calprotectin guides treatment escalation, monitors response to therapy, and predicts clinical and endoscopic relapse months before symptoms emerge.

Reference ranges

Standard reference

<50 µg/g in adults; age-specific thresholds apply in infants and young children.

Functional medicine optimal

Thresholds differ by clinical question. Many guidelines use <50 µg/g for normal, 50–250 µg/g as intermediate (often repeated or correlated with symptoms), and ≥250 µg/g as significantly elevated, warranting further investigation or endoscopy.

Units

µg/g, mg/kg

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.