The invention relates to a dose settingmechanism (4), which is operable to be coupled to a medicationcartridge (25) and which comprises means thatprevent the user from setting a dose greater than the remainingmedication in the cartridge (25). The dose settingmechanism comprises a shaft (30). A helical groove (32)having a first pitch is provided along a first portion (32) ofthe shaft (30). The dose setting mechanism (4) furthercomprises a nut member (40) disposed on the helicalgroove (32) of said shaft (30). During dose setting, theshaft (30) is rotated relative to the nut member (40) whilethe nut member (40) traverses along the groove (32) froma distal end (38) of the shaft (30) towards a proximal end(39) of the shaft (30). The mechanism further comprisesmeans preventing a user of said dose setting mechanism(4) from setting a dose of said medication that is greaterthan said remaining medication in said cartridge (25), saidmeans comprising a second pitch provided along a secondportion (36) of said shaft (30), wherein said first pitch isdifferent from said second pitch, wherein said secondpitch is preferably greater than said first pitch.
