An injection device including a volume for accommodating a product for administration, a piston for acting upon the product within the volume, and a stopper which can be arranged between an end of the piston facing the product and the product within the volume, wherein the piston includes a piston head configured to be sealed in a gas-tight manner, the piston head being separate from the stopper such that a negative pressure or vacuum region can be developed between the piston head and the stopper.