Drug delivery devices of a standard size are adapted for injecting different doses. The device comprises an injection needle, a reservoir having an available volume, and a plunger for evacuating the volume into the needle for injection. A spacer is placed with the plunger in the reservoir to take up some of the available volume and leave a residual amount of available volume in the reservoir to correspond to a currently desired dose size. The spacer may be selected from different sizes corresponding to different doses.
