An apparatus for extracorporeal blood treatment, comprising: a treatment unit; a blood circuit coupled to the treatment unit and comprising a blood removal line and a blood return line connectable to a vascular system of a patient; a blood pump configured to be coupled to a pump section of the blood circuit; an effluent line connected to the treatment unit; at least one infusion line (16, 17, 18, 25, 27) connected to the blood circuit and/or a dialysis line connected to the treatment unit; wherein the at least one infusion line (16, 17, 18, 25, 27) and/or the dialysis line are connected or connectable to at least one source (14, 19, 21, 23, 26, 28) of at least one fluid; a control unit connected at least to the blood pump characterized in that the control unit is programmed for receiving: a solute concentration (C soln) of at least one selected solute in the at least one fluid; at least one patient parameter related to a patient solute concentration (Cp soln) of the at least one selected solute in patient's blood; optionally said patient parameter being the patient solute concentration (Cp soln); a specific energy load (Emet soln) of the at least one selected solute; a measured or set fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) of the at least one fluid crossing the at least one infusion line (16, 17, 18, 25, 27) and/or the dialysis line; a measured or set filtration flow rate (Qfil) in the treatment unit or a measured or set patient fluid removal rate (Qpfr); the control unit being programmed for computing during the extracorporeal blood treatment a mass balance rate (J soln) of the at least one selected solute from the solute concentratior (C soln), from the patient parameter, from the fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) and from the filtration flow rate (Qfil) or the patient fluid removal rate (Qpfr); computing, from the computed mass balance rate (J soln) and from the specific energy load (Emet soln), an energy balance (E soln) due to the at least one selected solute during the extracorporeal blood treatment. a treatment unit; a blood circuit coupled to the treatment unit and comprising a blood removal line and a blood return line connectable to a vascular system of a patient; a blood pump configured to be coupled to a pump section of the blood circuit; an effluent line connected to the treatment unit; at least one infusion line (16, 17, 18, 25, 27) connected to the blood circuit and/or a dialysis line connected to the treatment unit; wherein the at least one infusion line (16, 17, 18, 25, 27) and/or the dialysis line are connected or connectable to at least one source (14, 19, 21, 23, 26, 28) of at least one fluid; a control unit connected at least to the blood pump characterized in that the control unit is programmed for receiving: a solute concentration (C soln) of at least one selected solute in the at least one fluid; at least one patient parameter related to a patient solute concentration (Cp soln) of the at least one selected solute in patient's blood; optionally said patient parameter being the patient solute concentration (Cp soln); a specific energy load (Emet soln) of the at least one selected solute; a measured or set fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) of the at least one fluid crossing the at least one infusion line (16, 17, 18, 25, 27) and/or the dialysis line; a measured or set filtration flow rate (Qfil) in the treatment unit or a measured or set patient fluid removal rate (Qpfr); the control unit being programmed for computing during the extracorporeal blood treatment a mass balance rate (J soln) of the at least one selected solute from the solute concentratior (C soln), from the patient parameter, from the fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) and from the filtration flow rate (Qfil) or the patient fluid removal rate (Qpfr); computing, from the computed mass balance rate (J soln) and from the specific energy load (Emet soln), an energy balance (E soln) due to the at least one selected solute during the extracorporeal blood treatment. a solute concentration (C soln) of at least one selected solute in the at least one fluid; at least one patient parameter related to a patient solute concentration (Cp soln) of the at least one selected solute in patient's blood; optionally said patient parameter being the patient solute concentration (Cp soln); a specific energy load (Emet soln) of the at least one selected solute; a measured or set fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) of the at least one fluid crossing the at least one infusion line (16, 17, 18, 25, 27) and/or the dialysis line; a measured or set filtration flow rate (Qfil) in the treatment unit or a measured or set patient fluid removal rate (Qpfr); the control unit being programmed for computing during the extracorporeal blood treatment a mass balance rate (J soln) of the at least one selected solute from the solute concentratior (C soln), from the patient parameter, from the fluid flow rate or rates (Qpbp, Qpre, Qpost, Qdial, Qanc) and from the filtration flow rate (Qfil) or the patient fluid removal rate (Qpfr); computing, from the computed mass balance rate (J soln) and from the specific energy load (Emet soln), an energy balance (E soln) due to the at least one selected solute during the extracorporeal blood treatment.