The present invention relates to an injector device (20) having a housing (21), a cartridge (22) having a reservoir (28) for medicament, a needle unit (23) comprising a needle (31), and an actuator (26). The needle unit (23) is movably mounted to the housing (21) and prior to use of the injector device the reservoir (28) is sealed from the needle (31). The actuator (26) is configured to move the needle unit (23) into engagement with the cartridge (22) such that the needle (31) is moved into fluid communication with the reservoir (28). A thread is arranged to cause rotation of the needle unit (23) as the needle unit (23) moves into engagement with the cartridge (22).