You must be enrolled in Medicare Part A and/or Part B to enroll in Part D. You are eligible for Medicare Part D (prescription drug plan) coverage if you are eligible for Medicare. If you are a U.S. citizen or qualified legal resident and meet one of the following, you may be eligible:
Age 65 or older
Younger than 65 with a qualifying disability
Any age with a diagnosis of End-Stage Renal Disease (ESRD) or Amyotrophic Lateral Sclerosis (ALS, also called Lou Gehrig’s Disease)
To qualify as a legal resident, you must have lived in the United States for at least 5 years in a row before applying for Medicare.