Medicare Part D is an optional add-on to Medicare coverage and is not mandatory. Subscribers may select Part D coverage when they first become eligible for Medicare, or they may join during later enrollment periods. However, waiting to sign up for Part D may require payment of late enrollment fees.
Part D is not the only prescription coverage available for Medicare subscribers. Medicare Advantage plans, also known as Medicare Part C, frequently have their own prescription drug benefits. These plans are private insurance plans whose premiums are partially or entirely covered by Medicare. In some cases, they may offer better coverage than Part D plans.