A visual identification coding for a cartridge or cartridge holder for use with a drug delivery device is described. The visual identification coding includes a cartridge containing a drug and a light source located on the cartridge to visually indicate that the correct cartridge has been inserted into the drug delivery device. The light source may be a light emitting diode (LED), a surface mount diode (SMD), or an organic light emitting diode (OLED). A cartridge holder may also be included to receive the cartridge. In another embodiment, the light source may be located on the cartridge holder or a dose setting member.
