What can the Leaky Gut Test tell you — and what not?

The Leaky Gut Test (intestinal permeability test) measures markers like zonulin or the lactulose/mannitol ratio in urine. Elevated levels may indicate impaired gut barrier function – a condition linked to inflammatory bowel disease, celiac disease, irritable bowel syndrome, and even systemic inflammation. However, the evidence is mixed: zonulin is not a specific marker, test methods vary widely, and standardized reference ranges are lacking. Therefore, the test cannot provide a definitive diagnosis; it only offers a hint of possible increased permeability. It should not be used as the sole basis for diets or supplements. Many providers over-market the test as a 'root cause finder' for fatigue, skin issues, or autoimmunity – there is insufficient scientific support for that. Clinically, a gastroenterologist should use established procedures (e.g., controlled lactulose/mannitol test) for assessment. Bottom line: The test can be a screening tool, but not a reliable diagnosis. Interpretation requires medical expertise and integration into the overall clinical picture.