A system for generating an indicator at least in part relating to fluid levels in a biological subject, the system including one or more processing devices that, in response to at least one impedance measurement performed on the subject determine a parameter value at least in part using results of the at least one impedance measurement, perform an assessment to determine if the parameter value is indicative of a meaningful change in a subject normal, the subject normal being based on results of a plurality of previous impedance measurements and use results of the assessment to generate an indicator indicative of fluid levels or selectively update the subject normal.
