A medication and needle module (20) for an injection device. The module (20) includes a housing (22) including a first portion (39) and a second portion (38) detachably connected together, the second housing portion having a periphery complementarily shaped with a cavity (154) in the injection device (150) to be loadable therein, a primary container (120) within the first housing portion and including a medication filled reservoir (124), a secondary container (70) within the second housing portion and including a medication tillable reservoir, a needle cassette (60) rotatably mounted within the second housing portion and including a plurality of delivery needles (64), and a transfer needle assembly (100) within the housing. The detachability of the second housing portion from the first housing portion permits the second housing portion with the secondary container and the needle cassette to be loaded as a unit independently of the first housing portion into the injection device cavity for use.