The scope of the invention is to apply an electric current or to use a kind of iontophoresis system with the hemodialysis cartridge and system (the proposed method is also applicable to peritoneal dialysis or other similar methods) to remove unwanted molecules from blood, plasma or serum or other body fluids and to increase the effectiveness of the process. This cartridge can be used for patients with uremia and cartridge fixed to the conventional hemodialysis machine and additionally the electric current applied to the electrodes placed in to the cartridge or electrode connectors placed to the conventional cartridge. When the system activated, the molecules in the blood or other body fluid migrates to the hemodialysis solution. Charged ions or uncharged molecules move together with electroosmotic flow. The sterilized electrodes preferably made by Ag/AgCl to prevent pH changing effect. Other apparatus can also be used for providing an electropotential gradient.