If you belong to a Medicare Advantage HMO or PPO, you can only get Medicare prescription drug coverage from your plan (if offered). If you join a stand-alone Medicare Prescription Drug Plan, you will be automatically disenrolled from your Medicare HMO or PPO and returned to the Original Medicare Plan.
(Primary Source: Centers for Medicare and Medicaid Services - Medicare and You Handbook. This content may have been enhanced by Q1Group LLC to include further examples, explanations, and links.)