Question: I'm billing oxygen therapy provided during an office visit for a Medicare patient. What CPT® should I use? What are the limitations set by Medicare on oxygen therapy coverage? Indiana Subscriber Answer: No CPT® code represents the administration of oxygen therapy. Don't report 94799 (Unlisted pulmonary service or procedure), because you must bill oxygen in measurable units (i.e., per liter, per hour). You would include this in your E/M service. Should the patient require home oxygen, the physician must certify the need for this, after meeting certain requirements (available in Chapter 20 of the Medicare Claims Processing Manual, http://www.cms.gov/manuals/downloads/clm104c20.pdf). Coverage: