The invention relates to an electrode system for measuring the concentration of an analyte under in-vivo conditions, comprising a counter-electrode (2) having an electrical conductor (2a), a working electrode (1) having an electrical conductor (1a) on which an enzyme layer (5) containing immobilized enzyme molecules for catalytic conversion of the analyte is arranged, and a diffusion barrier that slows the diffusion of the analyte from body fluid surrounding the electrode system to enzyme molecules down. The invention provides the enzyme layer (5) in the form of multiple fields that are arranged on the conductor (1a) of the working electrode (1 ) at a distance from each other.
