A spring assisted drug delivery device (80, 90, 100) is provided comprising a housing (4) and a lead screw (22) having a longitudinal axis, a distal end and a proximal end that is rotatably fixed during dose setting and dose delivery and axially moveable in a distal direction relative to the housing. The device further comprises a drive nut (23) threadedly engaged and screwable along the lead screw threaded shaft and a number sleeve (24) threadedly engaged with the housing (4) to be screwable relative to the housing (4). A dial link (25) is connected with the drive nut (23) and axially moveable and rotatably fixed relative to the drive nut (23) and an inner sleeve (29) is threadedly engaged with the number sleeve (24), the inner sleeve (2) being axially moveable and rotatably fixed relative to the housing (4). A mid-body (20) is axially fixed inside of the housing (4). A spring (82, 92, 102) is provided that assists a user of the device during a dose administration step.
