The invention relates to a device for receiving a body fluid, wherein the device comprises: a first chamber with a displaceable wall and a second chamber with a constant effective size, which is movable in relation to the displaceable wall, wherein the device is designed to connect the first chamber and the second chamber in the event of a longitudinal axial movement of the second chamber in relation to the displaceable wall and to transfer body fluid from the first chamber into the second chamber in the event of a movement of the second chamber together with the displaceable wall.
