16.2 Medicare Part C (Advantage) and Part D (Drug)

Medicare Part C (Medicare Advantage)

Part C, marketed as Medicare Advantage (MA), is an alternative way to receive Medicare benefits through private insurers approved by CMS. An MA plan must cover everything Original Medicare Parts A and B cover, and most bundle Part D drug coverage (a MA-PD plan) plus extras like dental, vision, hearing, and fitness benefits.

Eligibility and payment basics, often tested:

• The beneficiary must be enrolled in both Part A and Part B and live in the plan's service area.
• The beneficiary keeps paying the Part B premium and may owe an additional plan premium (often $0).
• Unlike Original Medicare, MA plans must include an annual out-of-pocket maximum for in-network Part A/B services.

Trap: A beneficiary cannot have a Medigap policy and a Medicare Advantage plan at the same time. Medigap only works with Original Medicare. Selling Medigap to an MA enrollee is an illegal sale.

MA Enrollment Windows and Disenrollment

Medicare Advantage uses its own enrollment calendar layered on top of the Part A/B timeline. The Annual Election Period (AEP) runs October 15 - December 7, when a beneficiary may join, switch, or drop an MA plan, with coverage effective January 1.

• The Medicare Advantage Open Enrollment Period (MA-OEP) runs January 1 - March 31, letting a current MA member switch to a different MA plan once, or return to Original Medicare.
• Special Enrollment Periods apply for moves out of the service area, loss of other creditable coverage, or qualifying life events.

Trap: Someone who returns to Original Medicare after trying Medicare Advantage may face medical underwriting when applying for Medigap, because the one-time Medigap Open Enrollment Period is usually long gone. A narrow trial-right guaranteed-issue rule protects only certain first-year MA switchers — timing matters.

Medicare Advantage Plan Types

MA plans use private-insurance network structures. Knowing each type's referral and network rules is exam-critical.

Original Medicare vs. Medicare Advantage: Original Medicare offers nationwide any-provider access but no OOP cap and requires a separate Medigap + Part D plan to control costs. Medicare Advantage offers a capped OOP and bundled extras but restricts you to networks and service areas. This trade-off — freedom vs. cost cap — is a recurring scenario question.

Medicare Part D: Prescription Drug Coverage

Part D provides outpatient prescription drug coverage through private plans, either as a standalone Prescription Drug Plan (PDP) added to Original Medicare or built into an MA-PD plan. Each plan publishes a formulary (covered-drug list) organized into tiers with different copays and uses utilization management tools like prior authorization and step therapy.

Part D enrollment and penalty rules:

• A beneficiary may enroll during the IEP, the Annual Election Period (AEP) of October 15 - December 7, or a qualifying SEP.
• Going 63 or more days without creditable drug coverage triggers a Part D late enrollment penalty, calculated as a percentage of the national base beneficiary premium and added for life.

Trap: "Creditable coverage" means coverage expected to pay at least as much as standard Part D. Employer drug coverage that is not creditable does not protect against the penalty.

Agents should also know that Part D is voluntary but penalized, while Part C is optional and unpenalized for the drug component when bundled. A beneficiary who keeps creditable employer or union drug coverage may delay Part D indefinitely and enroll later under a Special Enrollment Period with no penalty — the burden is on the plan to issue an annual creditable-coverage notice the beneficiary should retain as proof.

Part D Benefit Phases (Post-2025 Redesign)

The Inflation Reduction Act (IRA) restructured Part D. The old coverage gap ("donut hole") is eliminated and replaced by a hard annual out-of-pocket cap. Beneficiaries move through phases each calendar year.

Worked example: A beneficiary with high drug costs pays the deductible, then cost-shares through the initial phase. Once their true out-of-pocket spending hits the ~$2,000 cap, they pay nothing for the remainder of the year for covered Part D drugs — a dramatic change from the pre-2025 design where catastrophic-phase coinsurance continued.