System for determining heart failure indicator indicative of a heart failure disease state in a subject, including processing device(s) that at least in part control signal generator(s) and receives an indication of a measured response signal from sensor(s) allowing first and second impedance measurement(s) to be performed across at least one body segment, determines a first fluid level indicator using first impedance value(s) obtained by performing the first impedance measurement(s), the first fluid indicator being indicative of a first ratio of ECF to TBW at a first time, determines a second fluid level indicator using second impedance value(s) obtained by performing the second impedance measurement(s), the second fluid indicator being indicative of a second ratio of ECF to TBW at a second time, determines a fluid level change using a difference in the first and second fluid level indicators, and, determines the heart failure indicator using the fluid level change.
