Question: How should I code when our physician gives an injection of allergen immunotherapy with serum obtained from a doctor from another practice? Ohio Subscriber Answer: Family practitioners often administer antigens devised by an allergist or another doctor. If the other physician prescribed the medication, you should code 95115 (Professional services for allergen immunotherapy not including provision of allergenic extracts; single injection) or 95117 (... two or more injections), depending on the number of injections given. When your FP provides the allergenic extracts, use 95120 (Professional services for allergen immunotherapy in prescribing physicians office or institution, including provision of allergenic extract; single injection) or 95125 (... two or more injections).