Abstract: A monitoring system for monitoring the glucose level of a subject having a glucose level history is disclosed. The system comprises (a) a non-invasive measuring device, operable to measure and record an electrical quantity from a section of the subject body, so as to provide a time-dependence of the electrical quantity over a predetermined time-period. The system further comprises (b) a processing unit, communicating with the non-invasive measuring device. The processing unit comprises: an extractor, for extracting a plurality of parameters characterizing the time-dependence, a correlation function calculator for calculate a subject-specific correlation function, and an output unit, communicating with the correlation function calculator and configured to output the glucose level of the subject. The subject-specific correlation function describes the glucose level history and is defined over a plurality of variables, each corresponding to a different parameter.