A blood treatment device comprising a blood treatment unit (20) with a valve (6) configured to move between a first position and a second position, for opening and closing multiple sections in a blood withdrawal line such that double-needle dialysis is achieved. Alternatively, single needle dialysis is achieved by moving the valve between two specific positions. Still alternatively, it is also possible to achieve either double-needle or single-needle dialysis, as selected by an operator, by moving the valve between four positions.
