Either the patient or health care provider is responsible for getting prior authorization under Medicare. Original Medicare only requires prior authorization for certain services or items, though a required prior authorization list of durable medical equipment is under consideration as of 2015, notes the Centers for Medicare & Medicaid Services.
Medicare Part D prescription drug plans might require either the patient or prescribing provider to obtain prior authorization before filling certain prescriptions, notes Medicare.gov. The prescriber might need to prove the drug's medical necessity to the patient.
In some instances, prior authorization is necessary only for patients who reside in certain states. For example, Medicare does not require prior authorization for hyperbaric oxygen therapy unless the patient receives services in Illinois, Michigan or New Jersey, explains Medicare.gov.