16.2 Medicare Part C (Advantage) and Part D (Drug)
Key Takeaways
- Part C (Medicare Advantage) requires Part A and Part B enrollment and continued Part B premiums; it includes a mandatory out-of-pocket maximum.
- A consumer cannot hold both Medicare Advantage and a Medigap policy at the same time; they are alternatives.
- Part D is voluntary drug coverage via PDP or MA-PD plans using tiered formularies.
- The Part D late penalty is ~1% of the base premium per uncovered month after a 63-day gap, and it is permanent.
- MA/Part D elections occur during AEP (Oct 15-Dec 7) and MA-OEP (Jan 1-Mar 31).
Medicare Part C: Medicare Advantage
Medicare Part C, marketed as Medicare Advantage (MA), is private insurance that replaces the way Original Medicare delivers benefits. A beneficiary must already be enrolled in both Part A and Part B and must continue to pay the Part B premium. The private plan then administers the Medicare benefits, often adding extras such as dental, vision, hearing, and routine wellness.
Unlike Original Medicare, every Medicare Advantage plan must include an annual out-of-pocket maximum for Part A and Part B services. Most MA plans also bundle Part D drug coverage (called MA-PD plans).
Common Medicare Advantage Plan Types
| Plan type | Network rule | Out-of-network | Referral for specialist |
|---|---|---|---|
| HMO (Health Maintenance Organization) | Must use plan network | Generally not covered (except emergencies) | Usually required |
| PPO (Preferred Provider Organization) | Lower cost in-network | Covered at higher cost | Usually not required |
| PFFS (Private Fee-for-Service) | Provider must accept plan terms | Varies | Usually not required |
| SNP (Special Needs Plan) | Restricted to a qualifying group | Network-based | Often required |
Special Needs Plans (SNPs) serve only specific populations: people who are dual-eligible (Medicare + Medicaid), institutionalized, or have a qualifying chronic condition.
Medicare Advantage vs. Original Medicare + Medigap
This distinction is a frequent exam trap. A consumer cannot hold a Medicare Advantage plan and a Medicare Supplement (Medigap) policy at the same time. They are alternatives, not companions.
- Original Medicare + Medigap: any provider that accepts Medicare nationwide; predictable gap coverage; usually higher premium; no built-in drug plan (buy a stand-alone Part D).
- Medicare Advantage: network-based; lower or $0 premium beyond Part B; built-in out-of-pocket maximum; often includes drugs and extras; care is managed.
It is illegal for an agent to knowingly sell a Medigap policy to someone enrolled in a Medicare Advantage plan unless that person is disenrolling from the MA plan.
Medicare Part D: Prescription Drug Coverage
Part D is voluntary outpatient prescription drug coverage offered through private plans, either as a stand-alone Prescription Drug Plan (PDP) alongside Original Medicare or built into an MA-PD. Plans use a formulary (a tiered list of covered drugs).
Part D late-enrollment penalty: if a person goes 63 or more days without creditable coverage after their initial enrollment period, a permanent penalty is added — roughly 1% of the national base beneficiary premium for each full month without creditable coverage. Like the Part B penalty, it lasts for life.
The Part D Coverage Stages
Historically Part D had a coverage gap (the "donut hole"). Under current rules (post-2025 redesign), the gap is effectively closed and replaced by an annual out-of-pocket cap (illustrative $2,000 in 2026). The stages a beneficiary moves through are:
- Deductible stage: beneficiary pays 100% up to the plan deductible.
- Initial coverage stage: beneficiary pays a copay/coinsurance; plan pays the rest.
- Catastrophic stage: once total out-of-pocket drug spending reaches the annual cap, the beneficiary pays $0 for covered drugs for the rest of the year.
Trap: older study material still tests the "donut hole" terminology — know the concept, but recognize the modern out-of-pocket cap replaced it.
Worked Example: Part D Penalty
A beneficiary delays Part D for 20 months without creditable coverage. Assume the national base beneficiary premium is $36.00.
- Penalty = 1% x 20 months = 20% of the base premium.
- 0.20 x $36.00 = $7.20 added to the monthly Part D premium, rounded to the nearest $0.10.
- This $7.20 is added every month, for life, on top of whatever plan premium the person chooses.
Election timing: Medicare Advantage and Part D changes happen during the Annual Election Period (AEP), October 15 - December 7, and the Medicare Advantage Open Enrollment Period (MA-OEP), January 1 - March 31, when an MA enrollee may switch MA plans or return to Original Medicare.
Which statement about Medicare Advantage (Part C) is correct?
A beneficiary goes 20 months without creditable drug coverage and the national base premium is $36.00. What lifetime Part D penalty is added to the monthly premium?
Enrollment Windows for Part C and Part D
Medicare Advantage (Part C) and Part D drug plans share key enrollment periods that the exam loves to test:
| Period | When | What You Can Do |
|---|---|---|
| Initial Enrollment Period (IEP) | 7 months around the 65th-birthday month | First enroll in Part C/D |
| Annual Election Period (AEP) | Oct 15 - Dec 7 | Join/switch/drop Part C or D |
| Medicare Advantage Open Enrollment | Jan 1 - Mar 31 | Switch MA plans or return to Original Medicare |
To join a Part C or Part D plan, a person must first be enrolled in Part A and/or Part B and live in the plan's service area.
A Medicare beneficiary wants to switch from one Medicare Advantage plan to another. During which period is that allowed every year?
Part D Cost Structure and the Late-Enrollment Penalty
Part D drug plans move through stages: an annual deductible, an initial coverage phase, and a catastrophic phase with low cost-sharing after a spending threshold. (The old "donut hole" coverage gap has been largely closed.)
The late-enrollment penalty applies when a beneficiary goes 63+ consecutive days without creditable drug coverage after first becoming eligible. It is 1% of the national base beneficiary premium for each month without coverage, added to the Part D premium for life.
Worked example: 20 months late at a $34 base premium = 20% x $34 = about $6.80/month added permanently.
Exam Tip: "Creditable coverage" (drug coverage at least as good as Part D, e.g., from an employer) lets a person delay Part D without penalty.