A blood treatment apparatus adapted to preserve a blood treatment unit (20) between blood treatment sessions. The blood treatment apparatus is configured to i) perform a blood treatment session and thereby use the blood treatment unit (20), ii) fill the blood treatment unit (20) with a preservation fluid comprising at least one treatment fluid concentrate of a type that is used to prepare the treatment fluid, iii) maintain the preservation fluid in the blood treatment unit (20) until a next blood treatment session is prepared, iv) dispatch the preservation fluid from the blood treatment unit (20) in preparation of a next blood treatment session, and v) perform a next blood treatment session and thereby extend the use of the blood treatment unit (20). A related method is also described.