A medical sensor system for detecting at least one analyte in at least one animal and/or human body, said system comprising at least one sensor (14; 34), having at least one reservoir with at least one detection system for a measurement of the analyte, and at least one closure of the reservoir of the sensor (14; 34), wherein the closure is formed as a controllable organic membrane (20, 46), which has at least one pore (22, 48), the diameter of which is reversibly changeable, characterised in that the sensor system is designed in such a way that it either: - in a first step performs a reference measurement, wherein a first diameter of the pore of the controllable organic membrane is adjusted such that the analyte cannot infiltrate a sample volume of the reservoir and all molecules that are smaller than the analyte can infiltrate the sample volume, wherein, during the reference measurement by means of the detection system, interfering signals are determined as a measurement result of the reference measurement, and - in a second step an analyte measurement is performed, wherein a second diameter of the pore of the controllable organic membrane is adjusted so that the analyte can infiltrate the sample volume, wherein, during the analyte measurement by means of the detection system, the analyte is measured as a measurement result of the analyte measurement, and - the measurement result of the reference measurement is removed as background signal from the measurement result of the analyte measurement, whereby the sensor system determines an end measured value, or: - a reference measurement is performed, wherein a first diameter of the pore of a controllable organic membrane of a second sensor is adjusted so that the analyte cannot infiltrate a reference volume of a reservoir of the second sensor and all molecules that are smaller than the analyte can infiltrate the reference volume of the reservoir of the second sensor, wherein, during the reference measurement by means of the detection system, interfering signals are determined as a measurement result of the reference measurement, and - an analyte measurement is performed, wherein a second diameter of the pore of the controllable organic membrane is adjusted at the controllable organic membrane of the first sensor so that the analyte can infiltrate a sample volume of the reservoir of the first sensor, wherein, during the measurement by means of the detection system, the analyte is determined as a measurement result of the analyte measurement, and - the measurement result of the reference measurement is removed as background signal from the measurement result of the analyte measurement, whereby the sensor system determines an end measured value. - in a first step performs a reference measurement, wherein a first diameter of the pore of the controllable organic membrane is adjusted such that the analyte cannot infiltrate a sample volume of the reservoir and all molecules that are smaller than the analyte can infiltrate the sample volume, wherein, during the reference measurement by means of the detection system, interfering signals are determined as a measurement result of the reference measurement, and - in a second step an analyte measurement is performed, wherein a second diameter of the pore of the controllable organic membrane is adjusted so that the analyte can infiltrate the sample volume, wherein, during the analyte measurement by means of the detection system, the analyte is measured as a measurement result of the analyte measurement, and - the measurement result of the reference measurement is removed as background signal from the measurement result of the analyte measurement, whereby the sensor system determines an end measured value, - a reference measurement is performed, wherein a first diameter of the pore of a controllable organic membrane of a second sensor is adjusted so that the analyte cannot infiltrate a reference volume of a reservoir of the second sensor and all molecules that are smaller than the analyte can infiltrate the reference volume of the reservoir of the second sensor, wherein, during the reference measurement by means of the detection system, interfering signals are determined as a measurement result of the reference measurement, and - an analyte measurement is performed, wherein a second diameter of the pore of the controllable organic membrane is adjusted at the controllable organic membrane of the first sensor so that the analyte can infiltrate a sample volume of the reservoir of the first sensor, wherein, during the measurement by means of the detection system, the analyte is determined as a measurement result of the analyte measurement, and - the measurement result of the reference measurement is removed as background signal from the measurement result of the analyte measurement, whereby the sensor system determines an end measured value.