The invention relates to a measuring method and a measuring instrument for measuring raw data for determination of a blood parameter, in particular for non-invasive determination of the D-glucose concentration. The measuring device (1) comprises an excitation source (2) for generating electromagnetic radiation, a coupling arrangement (5-8) which is configured to couple in the radiation emitted by the excitation source (2) into a body surface of an object to be measured, and a sensor arrangement (13) which is configured to detect infrared (IR) radiation which is excited by the coupled-in radiation of the excitation source (2) in the body surface. The coupling arrangement (5-8) is configured to couple in the radiation emitted by the excitation source (2) extensively at a plurality of measuring points into the body surface, and the sensor arrangement (13) is configured to detect the IR radiation generated in the body surface at a plurality of measuring points.