A drive mechanism for a drug delivery device is presented having a housing, an axially displaceable piston rod to act on a piston of a cartridge containing a medicinal product to be dispensed, a drive member threadedly engaged with the piston rod and being slidably disposed relative to the housing between a distal stop position and a proximal stop position. During the setting of a dose the drive member is rotatable with respect to the housing and a dose dial member is operably engaged with the drive member by means of a reduction gear, wherein the drive member at its proximal end section comprises a radially extending receptacle adapted to receive the reduction gear.