An injection device (100), including a base (104), a sliding body (116) slidably connected to the base (104), a double-ended needle (120) fixed to the sliding body (116), a biasing member (124) for proximally biasing the sliding body (116) with respect to the base (104), and for retracting the needle (120) into the device (100) subsequent to activation of the device (100), a medicament cartridge (128) for holding a medicament, slidably connected to the sliding body (116), and a stopper (132) slidably disposed within the medicament cartridge (128). The base (104) has a proximal end (108) and a surface (164) disposed at a distal end (112) thereof for contacting a patient's skin. The base (104) also has a first locking mechanism. The sliding body, (116) has a locking feature and a second locking mechanism. The second locking mechanism locks the medicament cartridge (128) relative to the sliding body (116) upon completion of displacement of the medicament cartridge (128) relative to the sliding body (116). The first locking mechanism and the locking feature interact to lock the sliding member (116) relative to the base subsequent to retraction of the needle (120) into the device (100).
