System for extracorporeal blood treatment, with: A haemofiltration device, means for pumping blood through the haemofiltration device, citrate addition means arranged upstream of the haemofiltration device in the direction of blood flow configured to add citrate to the blood, calcium addition means arranged downstream of the haemofiltration device in the direction of blood flow configured to add calcium to the blood, and control means configured to activate or inactivate the citrate addition means and / or the calcium addition means, wherein the control means is adapted - to activate the citrate addition means at or before the beginning of blood treatment, - to continue to operate the citrate addition means until the end of blood treatment, at which point in time the citrate addition means is inactivated, characterized in that the control means is further adapted - to determine the elapse of a first time period after the blood treatment is activated, - to activate the calcium addition means after the first time period has elapsed, when total extracorporeal blood volume in the system has been filtered and citrate treated, - to continue to operate the calcium addition means in an active state during blood treatment to stably maintain a user-determined calcium addition rate, and - to continue to operate the calcium addition means in an active state after the end of blood treatment, until a second time period has elapsed after the end of treatment. A haemofiltration device, means for pumping blood through the haemofiltration device, citrate addition means arranged upstream of the haemofiltration device in the direction of blood flow configured to add citrate to the blood, calcium addition means arranged downstream of the haemofiltration device in the direction of blood flow configured to add calcium to the blood, and control means configured to activate or inactivate the citrate addition means and / or the calcium addition means, wherein the control means is adapted - to activate the citrate addition means at or before the beginning of blood treatment, - to continue to operate the citrate addition means until the end of blood treatment, at which point in time the citrate addition means is inactivated, - to activate the citrate addition means at or before the beginning of blood treatment, - to continue to operate the citrate addition means until the end of blood treatment, at which point in time the citrate addition means is inactivated, characterized in that the control means is further adapted - to determine the elapse of a first time period after the blood treatment is activated, - to activate the calcium addition means after the first time period has elapsed, when total extracorporeal blood volume in the system has been filtered and citrate treated, - to continue to operate the calcium addition means in an active state during blood treatment to stably maintain a user-determined calcium addition rate, and - to continue to operate the calcium addition means in an active state after the end of blood treatment, until a second time period has elapsed after the end of treatment. - to determine the elapse of a first time period after the blood treatment is activated, - to activate the calcium addition means after the first time period has elapsed, when total extracorporeal blood volume in the system has been filtered and citrate treated, - to continue to operate the calcium addition means in an active state during blood treatment to stably maintain a user-determined calcium addition rate, and - to continue to operate the calcium addition means in an active state after the end of blood treatment, until a second time period has elapsed after the end of treatment.