The gold standard for functional measurements of intestinal permeability in humans is the lactulose/ mannitol test, which measures urinary excretion of the two orally administered non-metabolized sugars over a 6 h period. Analysis by high pressure liquid chromatography or liquid chromatography in combination with mass spectrometry is usually performed on urine samples. The trait is fractional excretion of lactulose to mannitol ratio (EFO_0011032, an Experimental Factor Ontology id). Also known as: LacMan ratio, lactulose mannitol test.