The present invention refers to an injection device comprising a housing (6, 21), a cartridge holder (18) for receiving a cartridge (19) containing a medicament, the cartridge holder (18) having a first attachment member (18a), a threaded sleeve insert (12) axially and rotationally constrained to the housing (6, 21), threaded sleeve insert (12) having a second attachment member (12a) for releasable attachment of the cartridge holder (18) by means of interaction with the first attachment member (18a), and a metering mechanism. The metering mechanism comprises an actuating element (1) for setting or discharging a dose, a piston rod (2) for producing an advance movement for dispensing a dose, a piston rod sleeve (3) in which the piston rod (2) is accommodated such that the piston rod (2) can be non-rotatably connected to the piston rod sleeve (3), and a coupling element (4) with which the actuating element (1) and the piston rod sleeve (3) can be coupled for discharge of the dose set with the actuating element (1) in such a way that a dispensing movement of the actuating element (1) is transmitted to the piston rod (2) by way of the piston rod sleeve (3) connected to the piston rod (2). The piston rod (2) can be non-rotatably connected to the piston rod sleeve (3) by means of a coupling sleeve (7) wherein the coupling sleeve (7) can be in engagement with the piston rod sleeve (3) to form a non-rotatable connection between the piston rod (2) and the coupling sleeve (7) and wherein the coupling sleeve (7) can be out of engagement with the piston rod sleeve (3) such that the piston rod (2) is rotatable relative to the piston rod sleeve (3). According to the invention, attachment of the cartridge holder (18) to the threaded sleeve insert (12) includes an axial movement of the cartridge holder (18) with respect to the threaded sleeve insert (12) and the housing (6, 21), which axial movement brings the coupling sleeve (7) in engagement with the piston rod sleeve (3).La prése
