The invention relates to a test system for analyzing body fluids of the type comprising a test element tape carrying a plurality of test elements, a tape deflector for the test element tape for the selective application of body fluid, and a light source as well as a detector for optically analyzing test elements to which body fluid has been applied. The tape deflector has a rotatable optical element which acts as a deflection roller during transport of the test element tape. The optical element is positioned in the optical path between the light source and the detector.