Medicare Advantage

Medicare Advantage is the private-plan alternative to Original Medicare, established as Part C of Title XVIII of the Social Security Act at 42 U.S.C. 1395w-21 and following. The statute frames it as a choice: an eligible individual may receive benefits "through the original medicare fee-for-service program under parts A and B" or "through enrollment in" a plan under this part. A Medicare Advantage organisation contracts with the government to deliver the Part A and Part B benefits, and is paid a monthly amount per enrollee to do so.

The naming has a fossil in it that explains a great deal of confusing older material. The program was created as Medicare+Choice and renamed Medicare Advantage by the 2003 Medicare Modernization Act, but Congress did not rewrite every instance, so the operative eligibility definition in the code still reads "Medicare+Choice eligible individual". Sources written before 2004, and anything quoting the statute closely, use the older name for the same program.

🔴 Enrolment requires both Part A and Part B, and you keep paying for Part B. Section 1395w-21(a)(3) defines the eligible individual as one "who is entitled to benefits under part A and enrolled under part B". That is a stricter test than Part D's, which reaches someone entitled to Part A or enrolled in Part B. The practical consequence is the one most often lost in marketing: an Advantage plan is bought on top of the Part B premium, not instead of it. A plan advertising a zero-dollar premium is describing its own charge, and the Part B premium continues either way. Some plans do rebate part of it, which is a real benefit and a different thing from not owing it.

🔑 The out-of-pocket maximum is the structural reason the program exists. Under 42 C.F.R. 422.100(f)(4), a Medicare Advantage local plan must set an enrollee in-network maximum out-of-pocket amount for basic benefits no greater than an annual limit CMS calculates from Medicare fee-for-service data projections, and the organisation is responsible for tracking the enrollee's spending and alerting them and their providers when the amount is reached. Plans may set theirs lower, and many do. Original Medicare has no such ceiling of any kind, which is why the alternatives to it are effectively mandatory in practice even though they are optional in form. The dollar limit moves each year on the agency's own schedule, so medicare.gov is the place to read the current one.

What you give up is geography and permission. Original Medicare pays any provider that accepts Medicare, anywhere in the country, without a network. An Advantage plan is built around a service area, and section 1395w-21(b)(1) makes residence in that area a condition of enrolling. Within it, coordinated care plans may require prior authorization, subject to rules at 42 C.F.R. 422.138 confining its use to defined purposes such as confirming that the medical criteria for coverage are present. Prior authorization is not unknown in Original Medicare, which applies it to certain categories such as some hospital outpatient department services, but it operates on a far narrower set of items there and is not a general feature of getting care.

The plan types are not interchangeable. Section 1395w-21(a)(2) covers coordinated care plans, which include health maintenance organisations, provider-sponsored organisations and local or regional preferred provider organisations; medical savings account plans; and private fee-for-service plans. Specialised plans for people with particular needs sit inside the coordinated care category. The label matters because out-of-network coverage, referral requirements and whether drug coverage is included all differ by type, and two plans marketed side by side may not be comparable on any of them.

🔴 The initial choice is easier to make than to undo. Switching between Original Medicare and an Advantage plan is allowed in defined windows, so the Advantage side of the decision is reversible. What is not reliably reversible is the Medigap side. Medicare.gov states that the six-month Medigap open enrollment period beginning with the first month you have Part B and are 65 or older "is a one-time enrollment period. It doesn't repeat every year", and that afterwards "you may not be able to buy a Medigap policy, or it may cost more". Someone who takes an Advantage plan at 65 and wants Original Medicare with a supplement at 75 may find the supplement medically underwritten. Limited guaranteed-issue rights and some state protections exist, and they are narrower than most people assume.

Extras are real and bounded, and the way the plans are sold is part of the picture. Dental, vision, hearing and fitness benefits are genuine additions that Original Medicare does not offer, and they are typically allowances rather than comprehensive coverage, so the annual limit on each is the number that matters. On distribution, CMS regulates agent and broker compensation directly: since contract year 2025, under 42 C.F.R. 422.2274(d), organisations are limited to the compensation amounts the rule sets rather than deciding them by contract. The existence of that rule, and of the separate marketing rules alongside it, is a reasonable signal that the volume of advertising a plan receives is not evidence about the plan.

One benefit stays outside the plan. Under 42 C.F.R. 422.320, an enrollee who elects hospice remains enrolled in the Advantage plan and continues to receive everything that is not the hospice's responsibility through it, while the hospice care itself is paid outside the plan. It is the one part of the Part A benefit an Advantage plan does not deliver.

1. You qualify by being entitled to Part A and enrolled in Part B, and by living in the plan's service area.

2. You enroll in one plan, in an available window, and it becomes the way you receive your Part A and Part B benefits.

3. You keep paying the Part B premium, plus any premium the plan charges of its own.

4. You use the plan's network, and obtain prior authorization where the plan requires it.

5. Your in-network cost sharing accumulates toward the plan's annual out-of-pocket maximum, which the plan must track and tell you about.

6. The plan pays in full for covered in-network basic benefits once that maximum is reached, for the rest of the plan year.

A hypothetical, showing that the two routes differ in reversibility rather than only in price. Rosa turns 65 and compares two structures. Original Medicare plus a standalone drug plan plus a Medigap policy costs more every month, has no network, and has no ceiling of its own, the Medigap policy being what supplies the protection. A Medicare Advantage plan costs less every month, caps her in-network spending for the year, and confines her to its network and its authorization rules. Both require the Part B premium.

She takes the Advantage plan. Ten years later she moves to be near family, outside the plan's service area, and wants Original Medicare with a Medigap policy instead. Returning to Original Medicare is straightforward in an available window. Buying the Medigap policy may not be: her one-time six-month Medigap window opened when she first had Part B at 65 and closed six months later, so unless a guaranteed-issue right or a state protection applies, the insurer may underwrite her medically and may decline. Nothing about the first decision looked irreversible at the time, and the part that was irreversible was not the part she was choosing between.

Pros

• It supplies an annual out-of-pocket maximum, which Original Medicare does not have at all, and the plan must track it and tell you when you reach it.
• Drug coverage is usually bundled, so one plan and one card cover most of the ground.
• Premiums are often low or nil for the plan itself, since the government pays the organisation a monthly amount per enrollee.
• Dental, vision, hearing and similar extras are genuinely outside Original Medicare.
• Care is coordinated by one organisation, which for someone with several conditions and no strong provider preferences can be simpler than assembling the pieces.

Cons

• The network is the constraint, and it can change during the year. Care outside it may cost far more or not be covered at all, depending on plan type.
• Prior authorization applies to a far wider range of services than in Original Medicare, which can delay care as well as deny it.
• It cannot be combined with a Medigap policy, and returning to Original Medicare later may leave you medically underwritten for one.
• The extras are allowances rather than full coverage, and comparing them means reading the annual limit on each rather than the list of them.
• You still pay the Part B premium, which a zero-premium advertisement does not mention.
• Plans are local, so a move out of the service area forces a change whether or not you wanted one.