Medicare Advantage vs Medigap: Which Should You Choose?

How Medicare Advantage and Medigap Are Built

Medicare Advantage is a private plan that takes over your Medicare benefits entirely. Also called Part C, it's sold by an insurer under contract with Medicare, and it replaces Original Medicare rather than working alongside it.

Most Medicare Advantage plans also fold in Part D, the prescription drug benefit, so you carry one card and one insurer for hospital, medical, and drug coverage. Many build their network as a Health Maintenance Organization (HMO) or Preferred Provider Organization (PPO), which is how they control cost enough to often charge a $0 premium.

Medigap works the opposite way. You keep Original Medicare exactly as it is, Part A for hospital stays and Part B for outpatient care, and Medigap sits on top of it as a supplemental policy.

It pays some or all of the coinsurance, copayments, and deductibles Original Medicare leaves you owing. Medigap never replaces Original Medicare and never includes drug coverage, so a Part D plan is a separate purchase either way.

That structural split explains almost every other difference on this page. A private plan that controls your whole benefit can build a network and negotiate rates.

A supplement riding on top of an already-open system can't do that. It just pays the bill Original Medicare leaves behind.

What You Pay Monthly Versus What You Pay at the Doctor

Medicare Advantage usually wins on the sticker price. A large share of Medicare Advantage plans charge a $0 monthly premium beyond what you already pay for Part B, since the insurer earns its revenue from Medicare's per-member payment instead of your premium. The tradeoff shows up later, in copays, coinsurance, and a deductible you owe each time you actually use care.

Medigap flips that order. You pay a real premium every month, and in exchange most of your point-of-care costs drop close to zero. A Medigap Plan G policyholder, for example, owes nothing out of pocket for a hospital stay or a specialist visit once the annual Part B deductible is met.

Run the two structures side by side over a full year, not one visit. A healthy retiree who rarely sees a doctor often comes out ahead on Medicare Advantage's $0 premium. A retiree managing a chronic condition, with frequent specialist visits and a hospital stay some years, often comes out ahead on Medigap's flat, predictable premium instead, because copay after copay adds up fast.

Enrollment Windows and the Underwriting Risk If You Switch Later

Both types of coverage have a window where insurers must accept you no matter your health. For Medicare Advantage, that's the Annual Election Period every fall, October 15 through December 7, when anyone can join, switch, or drop a plan for the following year. Current Medicare Advantage members also get a second, narrower Medicare Advantage Open Enrollment Period from January 1 through March 31, letting them make one plan change or return to Original Medicare.

Medigap works differently, and this is the part that trips people up. You get a one-time, six-month Medigap Open Enrollment Period that starts the first month you're 65 or older and enrolled in Part B.

During that window, an insurer can't deny you a policy or charge you more because of a health condition, under Medicare.gov's guaranteed-issue rules. Miss that window, and in most states an insurer can run medical underwriting on a new Medigap application, deny coverage outright, or charge a higher premium based on your health history.

That asymmetry is the real risk in this decision. Moving from Medigap to Medicare Advantage is guaranteed every single fall. Moving the other way, from Medicare Advantage back to Medigap after your first year, is not guaranteed in most states unless you qualify for a specific guaranteed-issue right, such as your plan leaving your service area, or you use a trial right within your first 12 months on the plan.

Prescription Drug Coverage Isn't Automatic on Either One

Prescription drug coverage is the piece most new Medicare enrollees assume comes with everything. It doesn't, and the two paths handle it in opposite ways. Most Medicare Advantage plans bundle Part D directly into the plan, sometimes called an MA-PD plan, so one enrollment covers your drugs along with your medical care.

Medigap never includes drug coverage under any plan letter. Pairing Medigap with Original Medicare means enrolling in a separate, stand-alone Part D plan from a third insurer, which adds a third monthly premium on top of Part B and your Medigap policy. Skip Part D entirely under either path, with no other creditable drug coverage, and you risk a late-enrollment penalty added to your premium for as long as you stay enrolled.

Why Some Doctors Push Back on Medicare Advantage

What we see near-retirees comparing these two get wrong most often is treating a network restriction as a minor inconvenience rather than a real gatekeeper on care. Medicare Advantage insurers submitted nearly 53 million prior authorization requests on behalf of their members in 2024, up from 49.8 million in 2023, according to KFF's analysis of federal data. Original Medicare, by contrast, requires prior authorization for very few services.

That volume is why some physician practices limit how many Medicare Advantage patients they take, or drop specific plans' networks entirely. A doctor billing Original Medicare, with or without a Medigap-covered patient, gets paid Medicare's set rate with no prior authorization step for most visits. A doctor billing a Medicare Advantage plan may need approval before a scan, a procedure, or a referral goes through, which adds staff time nobody pays them extra for.

None of this means Medicare Advantage care is worse care. It means the administrative friction is real, and it sits mostly on the Medicare Advantage side of this comparison, not spread evenly across both.

When a Network Change Should Flip Your Decision

Medicare Advantage doesn't fit someone who spends part of the year in a second state, since most plans only cover routine, non-emergency care inside their service area. It also doesn't fit someone managing a serious chronic condition who wants to keep a specific out-of-network specialist regardless of cost, since that specialist may not be reachable through the plan's network at any price.

A few events should flip this verdict once you've made it. A plan network dropping your doctor mid-year, a move to a new service area the plan doesn't cover, or a new diagnosis that turns occasional care into frequent specialist visits are all real reasons to use the next Annual Election Period to switch, and to weigh Medigap's guaranteed-issue rules before that window closes. Run the numbers on your own situation before you commit either way with our long-term care cost calculator, since a gap in coverage costs far more than the premium difference between Medicare Advantage and Medigap. Neither plan covers custodial long-term care once a Skilled Nursing Facility stay passes day 100 — our protecting assets from a nursing home guide covers what actually pays for care after Medicare stops.

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