Fall open enrollment runs October 15 through December 7, and the choice between Medicare Advantage and Medigap is the single biggest financial fork in the road for anyone turning 65.
The other can leave you exposed to bills that climb every year.
Picking wrong can cost a retiree thousands annually — and in most states, you may not get a do-over.
Medicare Advantage (Part C) replaces Original Medicare with a private plan, often bundling drug coverage and extras like dental or gym memberships.
Premiums can run as low as $0 beyond your Part B charge.
But those plans control costs through networks, prior authorizations, and copays that apply every time you use care — with no annual ceiling on what you pay.
Medigap, also called a Medicare Supplement, works the opposite way.
You keep Original Medicare and add a private policy that covers most of the gaps — deductibles, coinsurance, the 20% that Medicare doesn't pay.
Monthly premiums run higher, often $100 to $200 or more depending on your state and plan letter.
In exchange, your out-of-pocket exposure becomes predictable.
Plan G, the most popular choice for new enrollees, leaves you responsible mainly for the Part B deductible.
Medigap insurers in most states can medically underwrite you after your initial six-month window around age 65.
Develop a health condition, and you may be denied a supplement for life.
Medicare Advantage lets you switch plans or return to Original Medicare during annual enrollment, but getting a supplement afterward is the hard part.
Only a handful of states — including New York, Connecticut, Massachusetts, and Maine — guarantee year-round access regardless of health history.
That asymmetry drives the standard advice: if you can afford the premiums and expect ongoing medical needs, many advisors suggest starting with a supplement while you're healthy and guaranteed acceptance.
Advantage plans tend to pencil out for healthier retirees who want low premiums and don't mind network restrictions.
Advantage enrollment now covers more than half of all eligible Medicare beneficiaries, and insurers have faced tighter scrutiny over prior authorization and billing practices.
Meanwhile, Medigap premiums rise with age and medical inflation — the same forces pushing up grocery bills and rent.
Neither option escapes health care inflation; they just distribute it differently.
Add up premiums, then stress-test against a bad year: a hospitalization, a specialist, a costly prescription.
Compare that total against the Advantage plan's out-of-pocket maximum, which can reach $8,000 or more in-network.
Call your state's Senior Health Insurance Information Program for free, unbiased counseling.
And if you're already enrolled, check whether your drug list or provider network changed for January.
The real question isn't which plan is cheaper in a good year.
Final Thoughts
It's which one you can live with in a bad one — and whether you can still switch if your health turns.