The invention relates to a method for detecting a malfunction of a sensor for measuring an analyte concentration in vivo, wherein a series of measurement signals is produced by means of the sensor, and a value of a noise parameter is continually determined from the measuring signals, the noise parameter indicating how severely the measurement is impaired by interference signals. According to the invention, continually determined values of the noise parameter are used to determine how quickly the noise parameter changes, and the rate of change of the noise parameter is evaluated to detect a malfunction.
