An at least partly implantable system for injecting a substance into the body of a patient is disclosed. The system comprises at least one infusion needle disposed at least partly within at least one housing with a tip end of the infusion needle arranged for penetrating an outer wall of the housing. The system further comprises at least one drive unit adapted to be implanted inside the body and a for advancing and retracting the tip end of the infusion needle so that the infusion needle penetrates, upon advancement, the outer wall to allow for injection of the substance.
