Medicare Advantage: Private Bundles That Now Cover the Majority

Medicare Advantage — Part C — is Medicare coverage delivered by a private insurer under contract with the Centers for Medicare & Medicaid Services. Enrollees give up direct fee-for-service Original Medicare in exchange for a bundled plan that pairs hospital, medical, and (usually) drug coverage with extra benefits. More than half of Medicare-eligible Americans are now enrolled in a Part C plan, which makes understanding the trade-offs a decision almost every 65-year-old will face.

How the plan is structured

Most Advantage plans are HMOs or PPOs. The carrier receives a fixed monthly capitation payment from CMS for every enrollee and, in return, assumes responsibility for the enrollee's covered care. Because the carrier keeps the difference between capitation and paid claims, plan design and utilization management directly shape profit. That structure is why the same insurer can offer a $0-premium plan in one county and a $90 plan the next county over — the underlying CMS payment differs.

To stay eligible you must remain enrolled in Medicare Parts A and B and continue paying the Part B premium. You cannot simultaneously hold a Medigap policy — Advantage is an alternative to, not a supplement for, Original Medicare.

The five plan types

• HMO. The most common. Requires a primary-care physician and referrals for specialists. Out-of-network care generally isn't covered except in emergencies.
• PPO. No referrals; out-of-network care is covered but at higher cost-sharing. Better fit for travelers and people with established out-of-area specialists.
• PFFS (Private Fee-for-Service). Sets its own reimbursement rates. Any Medicare-approved provider can choose whether to accept the plan on a per-visit basis. Shrinking share of the market.
• SNP (Special Needs Plan). Restricted to a specific population — dual Medicare/Medicaid eligibility (D-SNP), an institutional setting (I-SNP), or a chronic condition like diabetes or heart failure (C-SNP). Benefits and drug formularies are tailored to that group.
• MSA (Medicare Medical Savings Account). High-deductible plan paired with a savings account CMS funds. Rare, but useful for enrollees who prefer to self-manage routine spending.

What is different from Original Medicare

• Networks. Care is generally in-network only (HMO) or steeply cheaper in-network (PPO). Original Medicare has no network — any provider that accepts Medicare accepts your card.
• Prior authorization. Advantage plans routinely require approval before advanced imaging, post-acute care, and specialty drugs. Original Medicare does not.
• Extra benefits. Dental, vision, hearing, fitness, over-the-counter cards, and transportation are common. Original Medicare covers none of these.
• Out-of-pocket maximum. Advantage plans have an annual cap (federal maximum $9,350 in-network for 2025). Original Medicare has none unless paired with Medigap.
• Premium. Many plans advertise $0 monthly premium. You still pay the Part B premium ($185/mo standard for 2025).
• Drug coverage. Most Advantage plans include Part D. With Original Medicare, you buy a standalone Part D plan separately.

What Part C actually costs in 2025

The sticker price is only one line on a longer bill. Expect to encounter five cost buckets:

• Part B premium. $185/month standard in 2025; higher via IRMAA if your modified adjusted gross income exceeds $106,000 (single) or $212,000 (joint).
• Plan premium. $0 on many mainstream plans; up to $200+ on richer PPOs and SNPs.
• Copays and coinsurance. $0–$50 primary-care visits, $30–$75 specialist visits, and coinsurance (often 20%) for imaging, chemotherapy, and inpatient stays past a threshold.
• Drug tiers. Formulary tier drives your prescription copay; a tier-4 or tier-5 specialty drug can run $100–$500 per fill until you hit catastrophic coverage.
• Out-of-pocket max. Once you reach the plan's cap, in-network Part A and B costs are covered 100% for the rest of the year. Drugs sit under Part D's separate $2,000 annual cap in 2025.

When you can enroll or switch

Timing matters more than any single benefit. See our Medicare enrollment guide for the full calendar, but the windows most relevant to Advantage are:

• Initial Enrollment Period. The 7 months around your 65th birthday. Confirm you're eligible for Medicare before shopping plans.
• Annual Enrollment (AEP). October 15 – December 7 every year. You can join, switch, or drop a Part C plan for coverage starting January 1.
• Medicare Advantage Open Enrollment. January 1 – March 31. Already in an Advantage plan? You get one switch (to another Advantage plan or back to Original Medicare with a Part D plan).
• Special Enrollment Periods. Triggered by moves, losing employer coverage, plan terminations, 5-star plan availability, and other qualifying events.

Star Ratings

CMS scores every plan 1–5 stars annually on quality, member experience, and complaint volume. A 4- or 5-star plan qualifies for a bonus payment and a year-round special enrollment period. Plans below 3 stars for three consecutive years can be terminated. Star Ratings are a useful floor — a 2-star plan is a warning — but a 4-star rating doesn't guarantee your specialist is in-network next year.

Prior authorization and appeals

CMS's 2024 rule tightened prior-authorization standards, but denial rates still vary widely by carrier. Nationally, more than 80% of Medicare Advantage prior-authorization denials that are appealed are overturned. Beneficiaries have five levels of appeal, ending in federal district court. Track deadlines closely — most levels have 60-day windows.

A practical rule of thumb: if a denial arrives in writing, appeal it. If it arrives by phone, ask for it in writing first, then appeal.

Switching back to Original Medicare

You can leave Advantage during AEP or the MA Open Enrollment Period. The catch: in most states, once you've been on Advantage past your initial 12-month trial right, insurers can medically underwrite a Medigap application and decline you or price you up. Connecticut, Maine, Massachusetts, and New York offer year-round guaranteed issue; a handful of others offer limited windows. Check your state's rules before dropping Advantage if a chronic condition would make Medigap unaffordable.

When Advantage is the right choice

• You are comfortable inside a defined network.
• You want dental, vision, hearing or OTC benefits without buying separate policies.
• Your preferred physicians and hospitals are in-network and expected to remain so.
• You cannot afford or medically qualify for a Medigap policy in your state.

When Original Medicare with Medigap is the better fit

• You travel or split time across states and want nationwide access.
• You have a chronic condition or planned procedures that could trigger prior authorization.
• You value predictable out-of-pocket costs over lower premiums.
• You are still in your 6-month Medigap open enrollment window and can obtain a policy without medical underwriting.

Frequently asked questions

What is Medicare Advantage (Part C)?

Medicare Advantage is Medicare coverage delivered by a private insurer under contract with CMS. It replaces Original Medicare (Parts A and B) with a bundled plan that usually includes prescription drug coverage and extras like dental, vision, and hearing.

How much does Medicare Advantage cost in 2025?

Many Advantage plans advertise a $0 monthly premium, but you still pay the standard Part B premium of $185/month in 2025. Out-of-pocket costs are capped at $9,350 in-network for 2025 (the federal maximum); most plans set a lower cap.

What's the difference between Medicare Advantage and Medigap?

Advantage replaces Original Medicare with a private network-based plan and adds extras. Medigap sits on top of Original Medicare and pays your share of Part A and B costs, but does not include drug coverage or extras. You cannot have both at the same time.

Do Medicare Advantage plans require prior authorization?

Yes. Most Advantage plans require prior authorization for advanced imaging, post-acute care (skilled nursing, home health, inpatient rehab), and specialty drugs. Original Medicare does not. More than 80% of appealed denials are ultimately overturned, so appeal rights matter.

When can I enroll in or switch Medicare Advantage plans?

You can join during your Initial Enrollment Period around your 65th birthday, during Annual Enrollment (October 15–December 7), or during the Medicare Advantage Open Enrollment Period (January 1–March 31) if you already have an Advantage plan. Special Enrollment Periods apply for qualifying life events.

What are Medicare Advantage Star Ratings?

CMS scores every plan 1–5 stars annually across quality, member experience, and complaints. Plans rated 4 stars or higher qualify for bonus payments and a year-round Special Enrollment Period. Plans rated under 3 stars for three consecutive years can be terminated.

Can I keep my doctor with Medicare Advantage?

Only if your doctor is in the plan's network. HMOs generally require in-network care except in emergencies; PPOs allow out-of-network care at higher cost-sharing. Networks can change year to year, so re-check every fall.

What are the downsides of Medicare Advantage?

Narrower provider networks, prior-authorization requirements, plan changes each year, and the risk that dropping Advantage later may leave you unable to buy a Medigap policy without medical underwriting in most states.

Keep reading

• Medicare, the full primer — how Parts A, B, C, and D fit together.
• Medicare eligibility — who qualifies, when, and how.
• Medicare enrollment periods — every window and its deadline.
• Medigap — how supplement policies pair with Original Medicare.
• Part D — standalone drug coverage, formularies, and the 2025 $2,000 cap.
• Plan Finder — compare Advantage and Part D plans against your drug list.