When to use code 90784 when processing medical billing claims for emergency room injections can raise a lot of questions. If you fail to follow the exact criteria for reimbursements of these types of claims, you risk only receiving partial reimbursement for the services or an outright rejection of the claim. The question of when to use this code comes up when a hospital supplies an injection or antibiotic to a patient in an emergency department visit situation. Many medical billers believe 90874 should not be used in this situation because the physician has not actually purchased the drug, just administered. In all actuality, 90784 means- therapeutic, prophylactic, and diagnostic …