Method for the optimization of the consumption of dialysate in a blood treatment unit comprising the following steps: a) Preselection of an operating mode and a lowest acceptable value for a dialysis performance parameter; b) Determining the current measured values for the flows of the blood and the dialysate in the blood treatment unit; c1) Variation of the flow of the dialysis solution in the blood treatment unit during a dialysis session; c2) Measuring the UV absorbance of at least one uremic substance in the dialysate outflow or in the extracorporeal blood circulation of the blood treatment unit; d) Forwarding the measured values of the UV absorbance and the current measured values for the flow of the blood and the dialysate to a central processing unit; e) Determining, via the current measured values for the flow of the blood and the dialysate and the values of the UV absorbance in the central processing unit, a flow of the dialysis solution optimized on the consumption of dialysate, and/or the blood, and/or a relative ratio of the two flows within a QD/QB range determined for the selected operating mode range, for which a decrease of the flow of the dialysis solution is not followed by a decrease in the clearance, without falling as a consequence below the lowest acceptable value of the selected dialysis performance parameter, such that an optimal saturation of the dialysis solution with uremic substances results; or e') Determining, via the current measured values for the flow of the blood and the dialysate and the values of the UV absorbance in the central processing unit, a flow of the dialysis solution optimized on the consumption of dialysate, and/or the blood, and/or a relative ratio of the volumes throughput of the dialysate and of the blood within a VD/VB range determined for the selected operating mode without falling as a consequence below the lowest acceptable value of the selected dialysis performance parameter, and a decrease of the flow of the dialysis solution is not followed by a decrease in the clearance, such that an optimal saturation of the dialysis solution with uremic substances results; f) Displaying the determined change of the flow of the dialysis solution and/or of the blood at the central processing unit and/or automatic readjustment in accordance with the calculated change in the blood treatment unit; and g) Repeating the steps b) to f) after a respective predetermined time interval or time interval scheme until the end of dialysis session. a) Preselection of an operating mode and a lowest acceptable value for a dialysis performance parameter; b) Determining the current measured values for the flows of the blood and the dialysate in the blood treatment unit; c1) Variation of the flow of the dialysis solution in the blood treatment unit during a dialysis session; c2) Measuring the UV absorbance of at least one uremic substance in the dialysate outflow or in the extracorporeal blood circulation of the blood treatment unit; d) Forwarding the measured values of the UV absorbance and the current measured values for the flow of the blood and the dialysate to a central processing unit; e) Determining, via the current measured values for the flow of the blood and the dialysate and the values of the UV absorbance in the central processing unit, a flow of the dialysis solution optimized on the consumption of dialysate, and/or the blood, and/or a relative ratio of the two flows within a QD/QB range determined for the selected operating mode range, for which a decrease of the flow of the dialysis solution is not followed by a decrease in the clearance, without falling as a consequence below the lowest acceptable value of the selected dialysis performance parameter, such that an optimal saturation of the dialysis solution with uremic substances results; or e') Determining, via the current measured values for the flow of the blood and the dialysate and the values of the UV absorbance in the central processing unit, a flow of the dialysis solution optimized on the consumption of dialysate, and/or the blood, and/or a relative ratio of the volumes throughput of the dialysate and of the blood within a VD/VB range determined for the selected operating mode without falling as a consequence below the lowest acceptable value of the selected dialysis performance parameter, and a decrease of the flow of the dialysis solution is not followed by a decrease in the clearance, such that an optimal saturation of the dialysis solution with uremic substances results; f) Displaying the determined change of the flow of the dialysis solution and/or of the blood at the central processing unit and/or automatic readjustment in accordance with the calculated change in the blood treatment unit; and g) Repeating the steps b) to f) after a respective predetermined time interval or time interval scheme until the end of dialysis session.