The miniaturized injection device (1) for medical use comprises a tube (2) extending along a certain axis (A-A) and in which there is disposed at least one reservoir (12) for receiving a medicinal substance, the reservoir being connected to at least one needle (14). The needle is movable in the tube (2) along said axis (A-A) and the injection device (1) further includes a pump (13) interposed between the needle and the reservoir. The pump is controlled by a switch (21) that operates in response to the needle (14) moving in the tube along said axis (A-A).
