The invention relates to systems and methods for sensing fluid characteristics of peritoneal dialysate infused into and removed from a patient during treatment. The systems and methods include sensors, processors, and flow paths for determining patient health based on the fluid characteristics of the peritoneal dialysate. The system can be a peritoneal dialysis cycler which can include an infusion line； an effluent line； at least one pump positioned in the infusion and/or effluent line； and at least one sensor fluidly connected to the effluent line. The sensor can be at least one of a flow sensor, an ion selective electrode, a pH sensor, a pressure sensor, a refractive index sensor, and a temperature sensor. The method can include infusing peritoneal dialysate through an infusion line； removing peritoneal dialysate through an effluent line； and determining at least one fluid characteristic of the peritoneal dialysate in the effluent line.
