Abstract: The reservoir for blood withdrawal has a housing (1) and a displaceable piston (7) located therein by means of which, in the interior of the housing, a reservoir chamber (16) of variable size can be formed. A piston is coupled to an actuation device (11). Furthermore, the piston (7) is pressed by a first spring (14) into a closed position in which the reservoir chamber (16) has a minimum volume. The actuation device (11) and the piston (7) are loosely coupled to each other by a second spring (10), where the spring excursion of this spring (10) is smaller than the movement path (13) of the actuation device, so that, at the end of the movement, a forced coupling between the piston and the actuation device (11) occurs.