The invention relates to a device for the transcutaneous, in vivo measurement of the concentration of at least one analyte in a living organism, comprising a carrier which can be introduced into the organism, and a luminescence indicator which is immobilized on the carrier and which reacts to a change in the concentration of the analyte to be measured with a change in at least one optical property, wherein the luminescence indicator is transcutaneously connected to a source for providing the excitation radiation and a detector for detecting the measuring radiation. According to the invention, the luminescence indicator is immobilized on the outer circumference of a catheter, which is used to dispense a fluid medium, for example a medicament, into the organism or to suck up a body fluid.
