Medicare's annual open enrollment runs through December 7, and the choice between Medicare Advantage and Medicare Supplement plans will swing many household budgets by thousands of dollars next year.
The two paths look similar on a brochure but work nothing alike once medical bills arrive.
Medicare Advantage, known as Part C, bundles hospital, doctor, and often drug coverage into one plan run by a private insurer.
Premiums frequently sit near $0 on top of the standard Part B charge, which is $185 per month in 2025.
The catch hides in cost sharing: deductibles, copays, and an out-of-pocket maximum that can reach $9,350 for in-network care this year.
Medicare Supplement plans, also called Medigap, pay the leftovers that original Medicare does not cover.
A Plan G policy, among the most popular, covers nearly everything except the Part B deductible.
The tradeoff is price: premiums commonly run $130 to $250 per month depending on age, gender, and state, and they typically rise over time.
The math flips depending on how often you see a doctor.
A healthy retiree who rarely uses care can come out ahead on Advantage, banking the premium savings.
Someone managing diabetes, heart disease, or cancer can blow past those savings fast, since Advantage plans charge per visit while Medigap picks up the tab.
There is a trap that catches people every year.
Medigap insurers in most states can reject applicants or charge more based on health history after your initial enrollment window closes.
Switch to Advantage at 65 and try to move back to Medigap at 72 with a new diagnosis, and you may find the door locked.
Advantage plans, by contrast, must accept everyone who qualifies.
Advantage plans usually include Part D, but formularies and prior authorizations can limit which prescriptions get covered.
Standalone Part D pairs with Medigap and lets you shop drug coverage separately each fall, though premiums and drug tiers shift annually.
Advantage plans lean on HMOs and PPOs with provider lists, and referrals are often required.
Medigap works with any provider nationwide who accepts Medicare, a real advantage for snowbirds and anyone who travels.
Insurers are betting heavily on Advantage, and marketing has followed.
Roughly half of all eligible Medicare beneficiaries now enroll in Advantage plans, drawn by low premiums and extras like dental, vision, and gym memberships.
Those perks are real, but they are also the first thing cut when plans trim benefits to protect margins.
For anyone turning 65, the practical move is to price both options with actual doctors and prescriptions in hand, not generic estimates.
Call the providers you use, confirm they are in network, and add up premiums plus worst-case out-of-pocket costs.
Then decide whether you are buying predictability or buying savings.
Medigap's guaranteed acceptance window generally lasts six months starting the month you enroll in Part B at 65.
Miss it, and your health history follows you into every future application. **Our take:** Medicare Advantage sells low premiums, and Medigap sells certainty.
The right answer depends less on marketing and more on your health trajectory, your travel plans, and whether you can pass underwriting later.
Final Thoughts
Run the numbers before December 7, because this is one decision you cannot easily undo.