An autoinjector having a lower body (10； 1010) receiving a reservoir, a piston, a needle, an actuating sleeve (11； 1011) with a contact end to contact the user. The actuating sleeve is displaceable between projected positions and an actuation position, being in a first projected position prior to actuation of the autoinjector. The autoinjector also having an injection device (5, 8； 1005, 1008) and an injection lock. The actuating sleeve is automatically returns to the second projected position when the user removes the autoinjector from his body and is locked in this second projected position. The autoinjector includes an external shell (22； 1022) having a display window for indicating the actuation sequences, at least one display window (221； 1221； 1023) indicating to the user that the injection of the fluid product is finished.
