An extracorporeal blood treatment apparatus comprising: a blood treatment unit (2) having a primary chamber (3), to receive blood from a patient to be treated, and a secondary chamber (4) separated from the primary chamber (3) by a semipermeable membrane (5)； a hydraulic circuit (13) having a fresh fluid path (15), connectable to an inlet of the secondary chamber (4), and a used fluid path (18), connectable to an outlet of said secondary chamber (4) and configured to remove used liquid from the secondary chamber (4) and transport it to at least one drain (14), the hydraulic circuit (13) being configured to operate at least in a normal mode, in which the fresh fluid path ( 15) is connected to an inlet of a secondary chamber (4) of the treatment unit (2) and transports fresh treatment liquid to the secondary chamber (4), and in an isolated ultrafiltration mode, where the fresh fluid path (15) does not transport fresh treatment liquid to the secondary chamber (4), a control unit (10) configured to receive at least two general configuration values selected from the group comprising: * a prescription value for a time of total treatment during e l which the patient must undergo blood treatment, * a prescription value for a total withdrawal of fluid from the patient to be achieved towards the end of the total treatment time, * a prescription value for an average patient fluid withdrawal rate a maintain throughout the total treatment time； characterized in that the control unit (10) is further configured to execute an isolated ultrafiltration task comprising the steps of: * receiving values of at least two isolated ultrafiltration parameters selected from the group comprising: - a time of isolated ultrafiltration, which is a time interval during which the apparatus is requested to operate in said isolated ultrafiltration mode, - an isolated ultrafiltration volume, which is a volume of fluid to be removed from the patient while the apparatus is requested to operate in said i
