The invention relates to a dialysis device (1) having a dialysate circuit comprising a first dialyzer (3) and a second dialyzer (5) wherein the first dialyzer (3) is connectable to a blood circulation of a patient via a blood feed line (11) and a recirculation (13), an effluent for a retentate flow (Qeffluent) from the dialysate circuit to the second dialyzer (5) is provided and a permetate stream (Qout) of the second dialyzer (5) in the dialysate circuit is passed to the first dialyzer (3), the second dialyzer (5) comprising a filter membrane having a cut-off value of at least 500 Da and the first dialyzer (3) comprising a filter membrane having a cut-off value exceeding that of the second dialyzer (5).
