The present invention relates to a drug delivery device (5) comprising a housing (10) with a proximal end (30) and a distal end (22), a cartridge holder (14) adapted to retain a cartridge (16), the cartridge holder (14) comprising an at least partially transparent side wall (36), a piston rod (26), the piston rod (26) being adapted to drive a piston so as to engage the piston (28) into the cartridge (16), and a plurality of symbols (32) on the piston rod (26), the symbols (32) representing dosage information during operation of the drug delivery device (5) and being visible through a window aperture (40) in the housing (10). Furthermore, using a plurality of symbols (32) on a piston rod (26) to represent dosage information during operation of the drug delivery device (5) is disclosed.
