If you're turning 65 or reviewing your coverage during Medicare Open Enrollment, you've probably stared at two very different paths: Medicare Advantage (Part C) or Original Medicare paired with a Medigap supplement.
The pitch for Advantage sounds great — low or $0 monthly premiums, dental, vision, gym memberships.
The pitch for supplements is quieter: higher upfront costs, but fewer surprises.
The catch is that the cheaper-looking option isn't always the cheaper one.
Medicare Advantage plans are run by private insurers.
You typically pay the standard Part B premium plus whatever the plan charges, and many advertise $0 extra.
But that low premium comes with networks, prior authorizations, and copays that can add up fast.
A 2023 KFF analysis found that nearly half of Advantage enrollees paid nothing beyond the premium in a given year — but the other half did, and out-of-pocket maximums can run as high as $8,850 in-network for 2025.
With Medigap, you pay a monthly premium — often $100 to $200 or more depending on your state, age, and plan letter — but the plan picks up most or all of the 20% of costs Original Medicare doesn't cover.
You can see any provider who accepts Medicare, anywhere in the country.
That flexibility matters if you travel or snowbird.
The trade-off is predictable: Advantage tends to cost less month to month but more when you actually use care.
Supplements cost more monthly but cap your exposure tightly.
If you're healthy and rarely see doctors, Advantage can pencil out.
If you have chronic conditions, take expensive drugs, or want to avoid authorization fights, a supplement often wins.
One big rule trips people up: you can usually only buy a Medigap policy without medical underwriting during your initial enrollment window — the six months starting when you're 65 and enrolled in Part B.
Miss it, and an insurer can charge you more or deny you outright based on health history.
Advantage lets you switch plans annually, but going from Advantage back to a supplement later can be difficult and pricey in most states.
With Original Medicare, you'll need a standalone Part D plan, which adds a premium but lets you shop separately.
Check your medication list against each plan's formulary before deciding — a drug that's covered under one plan may cost hundreds more under another.
There's no universal answer, and anyone who tells you otherwise is selling something.
Run your own numbers: add up premiums, estimate copays for your typical year, and factor in your worst-case scenario.
Then check whether your doctors are in-network and whether you can handle referrals and authorizations.
The honest take: Advantage is built to look cheap on the brochure, and for some people it genuinely is.
Final Thoughts
But if you value predictability, wide provider access, and fewer hoops, the higher premium of a supplement can be the more honest deal.