CARD T254
Medicare Advantage (Part C)
A Medicare-approved private-plan way to receive Part A and Part B benefits, usually with Part D. Plan networks and cost rules may differ from Original Medicare.
How it works
Medicare Advantage delivers Part A and B benefits through a Medicare-approved private plan, usually with Part D included. Enrollees generally must have A and B, live in the service area, and continue paying the Part B premium. Networks, referrals, prior authorization, and plan cost sharing can apply. Plans have an annual limit on out-of-pocket spending for covered A/B services. Medigap does not supplement Advantage. ESRD no longer creates a blanket enrollment prohibition. [1] [3]
A beneficiary compares a network-based Advantage plan with Original Medicare plus separate supplemental and drug coverage.
Part C is an alternative way to receive Medicare benefits, not a supplement added to Original Medicare.
CARD T255
Medicare Part D
Medicare prescription drug coverage through approved private plans. Covered drugs and cost sharing depend on the plan and program rules. Beginning in 2025, the coverage-gap phase ("donut hole") was eliminated.
How it works
Part D helps pay for eligible outpatient prescription drugs through approved private plans. It can be purchased separately or included in many Medicare Advantage plans. Each plan has a covered-drug list, called a formulary, and cost levels, called tiers. Pharmacy networks and rules such as advance approval also affect costs and access. The coverage-gap phase, nicknamed the donut hole, ended in 2025. Covered-drug out-of-pocket spending now has an annual cap; premiums do not count toward it. After the initial enrollment period, going 63 consecutive days or more without Part D or other creditable drug coverage can lead to a late penalty, with exceptions. “Creditable” means expected to pay at least as much, on average, as standard Medicare drug coverage. [1] [3] [4] [5] [6]
Two plans cover the same medicine on different tiers. Comparing the formulary and pharmacy terms matters more than premium alone.
The old donut-hole phase is not a current Part D benefit phase.
CARD T256
Medicare Supplement (Medigap)
Private coverage helping pay specified costs left by Original Medicare. It is different from Medicare Advantage.
How it works
Medigap is private insurance that helps with specified Original Medicare cost sharing. It does not replace A and B, and modern policies do not include Part D drug coverage. The federal six-month open enrollment period starts the first month a person is both 65 or older and enrolled in Part B. During that window, health status cannot be used to deny a policy offered for sale or charge more on that basis. Other guaranteed-issue rights and state protections may apply. [1] [7]
A person turns 65 but delays Part B while working with qualifying employer coverage. The federal Medigap window is tied to the later Part B enrollment, not age alone.
Medigap open enrollment is different from Medicare’s annual fall enrollment period.
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Practice questions
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T254 · Medicare Advantage (Part C)
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T255 · Medicare Part D
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T256 · Medicare Supplement (Medigap)
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Sources & further reading
Original explanations and practice scenarios informed by the following regulatory, legal, and product resources. State examples are not presented as nationwide deadlines or requirements.