The present disclosure relates to a calculation device for determining an interdialytic sodium intake of a patient and/or for determining a non-osmotically triggered interdialytic liquid intake, including a storage device and/or an input device configured for storing or for entering parameter values of the patient; a computing device, configured for calculating the interdialytic sodium intake of the patient and/or for calculating his non-osmotically triggered interdialytic liquid intake; and an output device for outputting a signal for controlling or closed-loop controlling a communication device and/or a medical blood treatment apparatus.