Medicare Advantage (Part C) Explained: Networks, Costs and Rules

Medicare Advantage, also called Part C, is a different way to receive your Medicare benefits. Instead of Original Medicare paying claims directly, a private company approved by Medicare provides your Part A and Part B coverage, and usually Part D as well.

You still have Medicare when you join a Medicare Advantage Plan. What changes is who handles your coverage, which providers you can use, and how your costs are structured. This guide explains how these plans work, what they must cover, and what to check before you join.

This is general information, not insurance, financial or medical advice. This independent site isn't connected with Medicare, CMS or any insurance company, and it doesn't recommend or rate plans. For unbiased one-on-one help, contact your State Health Insurance Assistance Program (SHIP) or call 1-800-MEDICARE (1-800-633-4227).

How Medicare Advantage works

According to the Medicare & You 2027 handbook, Medicare Advantage Plans are Medicare-approved plans offered by private companies, and they must follow rules set by Medicare. Medicare pays the company a fixed amount each month for your coverage. Each plan can then set its own out-of-pocket costs and its own rules for getting care, and those can change every year. The handbook also notes that plan names don't always include the words "Medicare" or "Medicare Advantage."

To join, the 2027 handbook says you must have Part A and Part B, live in the plan's service area, and meet Medicare's citizenship or lawful-presence rules. You can join even with a pre-existing condition, but you can be in only one Medicare Advantage Plan at a time.

When you're a member, you use the plan's card for Medicare-covered services. Medicare.gov advises keeping your red, white and blue Medicare card somewhere safe, because you may need it for some services or if you switch back to Original Medicare.

What plans must cover, and what they may add

Medicare.gov says Medicare Advantage Plans must cover all emergency and urgent care and almost all medically necessary services Original Medicare covers. Some costs stay with Original Medicare even if you're in a plan. The 2027 handbook lists hospice care, kidney transplant costs and some costs for clinical research studies.

Many plans add benefits Original Medicare doesn't, such as some vision, hearing and dental care, gym memberships, rides to doctor visits, or over-the-counter items. The Medicare & You 2027 handbook says these extra benefits are generally limited, so check exactly what's included before you join. Some plans also offer extra benefits designed for people with certain chronic illnesses, but the handbook notes you may not find out whether you qualify until after you join.

What you pay

Costs vary widely from plan to plan. Based on the Medicare & You 2027 handbook, your costs depend on:

• The plan's monthly premium. Some plans have a $0 premium, the 2027 handbook notes, but you still pay your Part B premium. Some plans help pay all or part of the Part B premium.
• Any yearly deductible, plus the copayment or coinsurance for each service
• Whether you stay in the plan's network
• The plan's yearly out-of-pocket limit

That last item is a key difference from Original Medicare. The handbook says plans set a yearly limit on what you pay for Part A- and Part B-covered services, sometimes with separate limits for in-network and out-of-network care. Once you reach it, you pay nothing for covered services for the rest of the year. The handbook also says plans can't charge more than Original Medicare for certain services, including chemotherapy, dialysis, and days 21–100 of skilled nursing facility care.

One limit to keep in mind: you can't use a Medicare Supplement Insurance (Medigap) policy to pay Medicare Advantage costs, and you can't buy one while you're in a plan unless you're switching back to Original Medicare.

Networks, referrals and prior authorization

Most plans use provider networks. The Medicare & You 2027 handbook describes the main plan types:

• Health Maintenance Organization (HMO): You generally must use network providers, except for emergencies, out-of-area urgent care and temporary out-of-area dialysis. You usually need a primary care doctor and referrals to see specialists.
• Preferred Provider Organization (PPO): You can go out of network for covered services, usually at a higher cost.
• Private Fee-for-Service (PFFS): You can see providers who accept the plan's payment terms, and out-of-network providers may decline to treat you.
• Medical Savings Account (MSA): A plan with a yearly deductible, paired with a savings account the plan deposits money into. It doesn't include drug coverage.
• Special Needs Plan (SNP): For people with Medicaid, certain severe or chronic conditions, or institutional-level care needs. All SNPs include drug coverage.

Networks can change during the year. The 2027 handbook says providers can join or leave a plan's network at any time, and you generally can't change plans midyear because of that. Your plan must still give you access to qualified doctors and specialists. Medicare.gov adds that when a network provider isn't available or can't meet your medical needs, most plans will help you get medically necessary care out of network at in-network cost sharing.

Prior authorization is also more common than in Original Medicare. You or your provider can ask the plan in advance whether it will cover a service, which the handbook calls an "organization determination." If the plan says no, it must tell you in writing, and you can appeal. Medicare.gov says an approved prior authorization must stay valid for as long as the treatment is medically necessary. If you switch plans mid-treatment, Medicare.gov says you have at least 90 days before the new plan can require a new approval.

Check these before you join

• Your doctors and drugs. Medicare.gov's plan finder can show whether your providers are in network. Confirm with the provider too, and check the plan's drug list.
• Employer or retiree coverage. The 2027 handbook warns that joining a Medicare Advantage Plan might cause you, your spouse and your dependents to lose employer or union coverage, and you may not get it back. Call your benefits administrator first.
• An existing Medigap policy. If you drop Medigap to join a plan, the 2027 handbook says you may not be able to get it back, or you may pay more for a policy later, depending on your state's rules.
• Travel. Medicare.gov says plans generally don't cover care outside the U.S., though some offer emergency coverage abroad as an extra benefit.
• Yearly changes. The 2027 handbook says plans send an Annual Notice of Change by September 30 each year. Plans can also leave Medicare, in which case you'd choose another plan or return to Original Medicare.

Know the marketing rules

Medicare Advantage is heavily marketed, so it helps to know what's not allowed. Medicare.gov says plans and their agents and brokers can't:

• Call or text you unless you're already a member or gave permission
• Come to your home uninvited to sell you something
• Ask for bank or credit card information just to give you a quote
• Offer cash, gifts worth more than $15 (Medicare.gov's limit as of October 2026), or free meals as an incentive to join
• Use misleading information, including misleading use of the Medicare logo or card
• Pressure you to join or charge an enrollment fee

Medicare.gov also says independent agents and brokers must be licensed by your state. If someone breaks these rules or you think you were misled, call 1-800-MEDICARE. Never give your Medicare Number to someone who contacts you unexpectedly.

Key takeaways

• Medicare Advantage is a Medicare-approved private plan that bundles Part A, Part B and usually Part D. You're still in Medicare.
• Plans must cover almost everything Original Medicare does and often add limited extras, but networks, referrals and prior authorization rules vary.
• Unlike Original Medicare alone, every plan has a yearly out-of-pocket limit for Part A and Part B services, and you still pay the Part B premium.
• Check your doctors, drugs, any employer coverage and any existing Medigap policy before you join.
• Plans and agents must follow Medicare's marketing rules. Unsolicited calls, home visits and pressure tactics are red flags.

Sources

• Medicare.gov, How does Medicare work?
• Medicare.gov, Your health plan options
• Medicare.gov, Compare Original Medicare & Medicare Advantage
• Medicare.gov, Special Needs Plans (SNP)
• Medicare.gov, Marketing rules for Medicare health & drug plans
• Centers for Medicare & Medicaid Services, Medicare & You 2027 (official U.S. government Medicare handbook)