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  • This test measures the ability of two sugar molecules, lactulose and mannitol, to permeate the intestinal epithelial barrier. Ordinarily, mannitol is efficiently absorbed but lactulose, a larger molecule, is not. This test can help to identify malabsorption and “leaky gut” syndrome (abnormal intestinal permeability), which is often associated with inflammation specifically in the gastrointestinal tract.
  • This test requires a six-hour timed urine collection after ingesting a lactulose and mannitol solution.