A medical device (100) includes an insulin pen (102), a pen needle (104) and a force sensor (106). The device also includes a microprocessor (206) to receive a signal from the force sensor (106). Audible and/or visual indicators (218, 220) provide feedback to a user to encourage proper injection technique. The device may also include an adaptor assembly comprising a sensor housing (306) and a first sensor (304) within the sensor housing, and a transfer needle assembly (308), the transfer needle assembly providing a connection (310) for a pen needle, and providing a fluid conduit between the pen needle (312) and the insulin pen (302). A second force sensor (314) is associated with a thumb button of the insulin pen (302).