An injection device and an injection device trainer for training a user to use an injection device. Each one of the injection device and the injection device trainer can include: a body portion； an actuator positioned towards a proximal end of the body portion, the actuator moveable from a proximal position to a distal position； a shield positioned towards a distal end of the body portion, the shield moveable between: an initial position； a retracted position that is more proximal relative to the body portion than the initial position； and an extended position that is more distal relative to the body portion than the initial position； and a locking member rotatable between a first orientation in which the locking member resists movement of the actuator from the proximal position to the distal position； and a second orientation in which the locking member permits the actuator to move from the proximal position to the distal position.
