A method and system for proving a cannula arrangement (4) for an injection device. The cannula arrangement comprises a limiting element (16) and a housing configured to attach to the injection device. The housing and the limiting element define a compressible reservoir (40). A second medication (26) is provided in the reservoir. A first cannula (12) comprises a piercing end (20) configured for fluid engagement with a medication provided in the injection device and a distal end (22) configured for fluid engagement with the reservoir. A second cannula (14) comprises a proximal end (48) for fluid engagement with the second medication and a piercing distal end (50) for the injection to a patient.
