A manual injection device having a lower body and a fluid reservoir that moves axially in the lower body. The reservoir includes a piston and needle； an upper body mounted to move axially relative to the lower body, the upper body including a piston rod co-operating with the piston； and a sleeve mounted to move relative to the lower body between a rest position and a projecting position. The sleeve is blocked in its rest position before the injection device is actuated, and urged automatically into its projecting position after injection. The piston rod co-operates with the reservoir to form an injection lock, the force for moving the reservoir axially being less than the force for triggering the injection lock, such that pricking is performed before injection. Before actuation, the piston rod is connected to a ring that is fastened on a radial collar of the reservoir.
