Medicare Part C, officially called Medicare Advantage, is a bundled alternative to Original Medicare offered by private insurance companies approved by Medicare. Instead of getting hospital coverage (Part A) and medical coverage (Part B) separately through the federal government, you get both through a single private plan. Most Medicare Advantage plans also include prescription drug coverage (Part D), and the majority offer extras like dental, vision, and hearing benefits that Original Medicare doesn’t cover at all.
How Part C Differs From Original Medicare
With Original Medicare, the federal government pays your doctors and hospitals directly. You can see any provider in the country who accepts Medicare, with no referrals needed. But there’s no cap on what you might spend out of pocket in a given year, and you get no dental, vision, or hearing coverage.
Medicare Advantage flips several of those trade-offs. Plans are required to set an annual out-of-pocket maximum, which in 2025 cannot exceed $9,350 for in-network services or $14,000 for in-network and out-of-network services combined. Once you hit that ceiling, the plan covers everything else for the rest of the year. Original Medicare has no equivalent limit. The catch is that most Medicare Advantage plans restrict you to a network of providers, and some require referrals to see specialists.
Types of Medicare Advantage Plans
Not all Part C plans work the same way. The three most common structures are HMOs, PPOs, and Private Fee-for-Service plans, and they differ mainly in how much flexibility you have to choose your doctors.
HMO Plans
Health Maintenance Organization plans are the most restrictive. You generally must use doctors, hospitals, and other providers within the plan’s network, except for emergencies, urgent care when traveling, or dialysis away from home. Most HMOs also require a referral from your primary care doctor before you can see a specialist. Some plans offer an HMO Point-of-Service option that lets you go out of network for certain services, though you’ll pay more for doing so.
PPO Plans
Preferred Provider Organization plans give you more freedom. You can see any provider in the network at lower cost, but you’re also allowed to go outside the network. You’ll pay higher copays or coinsurance for out-of-network care, but you won’t need a referral for specialists.
PFFS Plans
Private Fee-for-Service plans are the most flexible. You can visit any Medicare-approved provider who accepts the plan’s payment terms and agrees to treat you. No referrals are required. If the plan has a network, you can use those providers too, though going out of network may cost more. The trade-off is that not every doctor will accept a PFFS plan’s terms, so you may need to confirm before scheduling an appointment.
Special Needs Plans
A subset of Medicare Advantage plans called Special Needs Plans (SNPs) are designed for people with specific health situations. There are three types. Dual Eligible SNPs (D-SNPs) serve people who qualify for both Medicare and Medicaid, helping coordinate benefits between the two programs. Chronic Condition SNPs (C-SNPs) limit membership to people with particular severe or chronic diseases, or a group of related conditions. Institutional SNPs (I-SNPs) are built for people living in facilities like nursing homes. Each type tailors its benefits, provider networks, and care coordination to its specific population.
Prescription Drug Coverage
Most Medicare Advantage plans bundle prescription drug coverage directly into the plan. These are labeled MA-PD plans (Medicare Advantage Prescription Drug plans). When your drug coverage is included, you use one plan and one card for medical care and prescriptions alike. One important rule: if your Medicare Advantage plan already includes drug coverage, you cannot also enroll in a separate standalone Part D drug plan. If you do, you’ll be disenrolled from your Medicare Advantage plan entirely and returned to Original Medicare.
A small number of Medicare Advantage plans don’t include drug coverage. If you join one of those, you can pair it with a standalone Part D plan.
Extra Benefits Beyond Original Medicare
One of the biggest draws of Medicare Advantage is access to supplemental benefits. Most plans offer some combination of routine dental care, eye exams and eyeglasses, hearing tests and hearing aids. Many also include fitness programs, transportation to medical appointments, over-the-counter health product allowances, and telehealth services. The specific extras vary widely by plan and region, so two Medicare Advantage plans in the same zip code may offer very different packages.
What You’ll Pay
Enrolling in Medicare Advantage does not replace your Part B premium. You must continue paying your standard Part B premium (or your income-adjusted amount if that applies to you) regardless of which Medicare Advantage plan you choose. On top of that, many plans charge their own monthly premium, though a significant number of plans have $0 premiums.
Your actual costs during the year depend on the plan’s copays, coinsurance, and deductibles for various services. These vary plan to plan. The out-of-pocket maximum described earlier provides a hard ceiling, but your day-to-day costs for office visits, hospital stays, and prescriptions will differ based on the specific plan you select.
Prior Authorization Requirements
One area where Medicare Advantage plans differ noticeably from Original Medicare is prior authorization. Many plans require you (or your doctor) to get approval before certain procedures, tests, or treatments are covered. This is meant to confirm that the service is medically necessary, but it can sometimes delay care.
Recent federal rules have tightened the guardrails around this process. Medicare Advantage plans must now follow the same national and local coverage decisions that apply in Original Medicare, meaning they can’t deny coverage for something that Original Medicare would approve. Plans are also required to give new enrollees a 90-day transition period: if you’re in the middle of an active course of treatment when you switch plans, your new plan cannot require prior authorization for that treatment during the first 90 days. Each plan must also maintain a committee that reviews its prior authorization policies annually to ensure they stay consistent with Original Medicare’s standards.
How Plans Are Rated
Medicare assigns every Advantage plan a Star Rating from 1 to 5 stars. These ratings are based on dozens of quality and performance measures. For plans that include drug coverage, up to 43 individual measures are evaluated. These cover a wide range: whether the plan helps patients manage diabetes and blood pressure, how quickly members can get appointments, how the plan handles appeals, customer service quality, hospital readmission rates, and whether members choose to stay in the plan or leave.
Plans with 4 or more stars are considered high-performing, and they receive bonus payments from Medicare that often translate into richer benefits for members. Checking Star Ratings on Medicare.gov before enrolling is one of the most practical ways to compare plans in your area.
Who Can Enroll and When
To join a Medicare Advantage plan, you need to be enrolled in both Medicare Part A and Part B, and you must live in the plan’s service area. Most people enroll during the Annual Enrollment Period, which runs from October 15 through December 7 each year, with coverage starting January 1. You can also enroll when you first become eligible for Medicare during your Initial Enrollment Period, which is a seven-month window surrounding your 65th birthday.
Outside those windows, Special Enrollment Periods let you make changes if specific life events occur: moving to a new address outside your plan’s service area, losing other health or drug coverage, entering or leaving a nursing home, or experiencing certain other qualifying circumstances. During January 1 through March 31 each year, people already in a Medicare Advantage plan can switch to a different Medicare Advantage plan or return to Original Medicare.