The invention relates to systems and methods for making intracycle adjustments to an osmotic agent concentration of peritoneal dialysate inside the peritoneal cavity of a patient. The systems and methods include osmotic agent sources, flow paths, and processors to adjust the osmotic agent concentration of dialysate in the peritoneal cavity of the patient. The method can include infusing peritoneal dialysate containing an osmotic agent into the peritoneal cavity of a patient; monitoring one or more patient parameters; and adjusting the osmotic agent concentration of the peritoneal dialysate in the peritoneal cavity of the patient by infusing a concentrated osmotic agent solution or by infusing sterile fluid into the peritoneal cavity of the patient using an on-line peritoneal dialysis machine. The system can include a peritoneal dialysis cycler.