An electrically-powered device intended to be used in a clinical setting to measure the concentration of exhaled hydrogen (H2) in end-tidal breath using electrochemical analysis, typically to assist with the diagnosis of intolerance and/or malabsorption of carbohydrates and/or intestinal bacterial overgrowth. It consists of a hand-held sensor unit with controls, display, and a breathing mouthpiece; a face mask and/or filter may be included.