A sensor system comprising a sensor carrying element (24) that is made of a flexible foil, and a sensing electrode (32), a counter electrode (34), and a reference electrode (36) that are positioned at one end (44) of the carrier (24) inserted into the tissue, where the electrodes (32,34,36) are connected to the opposite end (42) of the carrying element (24), located outside the body, with conductor paths (38) and a fluid duct (28) for the supply with insulin or the removal of a body fluid is guided from the exterior segment (42) into the tissue, is new.