An automatic drug delivery device is described, comprising: a housing (1); a skin sensor element (15) coupled to the housing and movable relative to the housing, wherein the skin sensor element is biased into a front position relative to the housing and is movable to a rear position relative to the housing when the skin sensor element is pressed against an injection site; a needle assembly comprising a hypodermic needle (11), the hypodermic needle extending outside of the housing when the device is in a needle insertion configuration; a drug delivery mechanism comprising a stored energy source (4), within the housing; wherein the drug delivery mechanism is released when the skin sensor element is moved from the front position towards the rear position and wherein the stored energy source is arranged to expand along an axis that is offset from an axis of travel of the needle assembly in use; a needle retraction mechanism configured to withdraw the hypodermic needle into the housing when the needle retraction mechanism is released; wherein the needle retraction mechanism is coupled to the skin sensor element such that when the skin sensor element is moved from the rear position towards the front position, and the needle is in the needle insertion position, the needle retraction mechanism is released.