An injection device having an inlet, an outlet and a chamber extending between the inlet and the outlet. A piston divides the chamber into an upper chamber and a lower chamber. The piston is movable within the chamber and includes a body. The piston includes a shutter movable with respect to the body between a closed position, wherein the body and the shutter isolate the upper chamber from the lower chamber when the piston is moved in an injecting direction, and an open position, wherein the body and the shutter place the upper chamber in fluidic communication with the lower chamber when the piston is moved in a filling direction.