Disclosed is an auto-injector which includes a housing adapted to receive a fluid container having a discharge nozzle and a dispensing piston moveable in the fluid container to expel the contents of the fluid container out of the discharge nozzle. The auto-injector includes a drive adapted on activation to act on the fluid container to advance it from a retracted position in which the discharge nozzle is contained within the housing to an extended position in which the discharge nozzle extends from the housing. The drive acts on the dispensing piston to expel the contents of the fluid container out of the discharge nozzle. The auto injector also includes a connector adapted to receive a vial containing fluid and connect it to the discharge nozzle. The auto-injector also includes means to move the dispensing piston relative to the fluid container from a first position in which the dispensing piston is located in the fluid container adjacent the discharge nozzle, to a second position in which the dispensing piston has been drawn away from the discharge nozzle. As the piston transitions from the first position to the second position fluid is drawn from the vial into the fluid container. The connector is a removable cap located over the discharge nozzle on the auto-injector. The cap has an open end which is adapted to receive the vial. The removable cap is adapted such that removal of the cap from the housing detaches the vial from the discharge nozzle.
