Apparatus (1) for delivering therapeutic fluid into a body of a patient, comprising: a dispensing unit (10) having a reservoir (220) containing therapeutic fluid, said dispensing unit (10) further comprising a driving mechanism (120) and an outlet port (210), with said driving mechanism (120) causing displacement of the therapeutic fluid disposed inside said reservoir (220) toward said outlet port (210)； a skin adherable needle unit (20) in fluid communication with said dispensing unit (10)； and a penetrating cartridge (22) having a penetrating member (320) and a cannula (330) for inserting into the body of the patient. The dispensing unit (10) can be connected to and disconnected from said skin adherable needle unit (20), and said outlet port (210) is configured to connect to and disconnect from said needle unit (20) establishing fluid communication between the reservoir (220) and the cannula (330) via a connecting lumen. The dispensing unit (10) further comprises: a reusable part (100) having at least part of said driving mechanism (120) and electronic components (130)； a disposable part (200) having said reservoir (220) configured as a unitary portion of a housing of said disposable part； and an energy supply means (240) electrically coupled to at least one of said electronic components (130) for supplying energy upon connection of said reusable part (100) and said disposable part (200).
