An at least partly implantable system for injecting a substance into a patient's body. The system comprises at least one implantable infusion needle (11) with a tip end (13) for injecting a substance into a penetration area of a patient. The system further comprises at least one drive unit (D) arranged for moving the tip end of the at least one infusion needle for changing the penetration area. The at least one drive unit is a drive unit arranged for moving the tip end of the at least one infusion needle using hydraulic force.
