A method performed on a dialysis machine includes receiving a first value that represents a pre-dialysis body weight of a patient and receiving a second value that represents a volume of liquid (V) inside a body of the patient. The method also includes administering dialysis to the patient, calculating an instantaneous body weight (W) of the patient based at least in part on the first value, determining a length of time (t) for which the dialysis was administered to the patient, determining a dialyzer clearance (K) associated with the dialysis, and calculating, based at least in part on the length of time, the instantaneous body weight, the volume, and the dialyzer clearance, a urea reduction ratio (URR) associated with the dialysis.
