The present invention provides a puncturing system for withdrawing body fluid. The puncturing system comprises a disposable puncturing unit, which includes a needle element for piercing into skin and a puncturing depth reference element with a skin contact area. The system includes a puncturing instrument which has a puncturing drive, wherein the puncturing drive is coupled by a coupling mechanism to the puncturing unit for driving the needle element to a puncturing depth, the puncturing depth being determined by the distance in the piercing direction between the skin contact area and the position of the tip of the needle at a reversal point of the puncturing movement. The puncturing depth reference element is connected to the needle element such that the puncturing depth reference element moves with the needle element during at least part of the puncturing movement. The puncturing depth reference element has a defined longitudinal position in the piercing direction relative to the needle element at least at the reversal point of the puncturing movement.