Open enrollment season is here, and millions of Americans on Medicare are staring at the same fork in the road: a Medicare Advantage plan with a tempting $0 premium, or a Medigap supplement with a monthly bill that can run $150 to $300 or more.
The difference between these two paths isn't just paperwork.
It's how much you pay when something actually goes wrong.
Medicare Advantage, also called Part C, replaces Original Medicare with a private plan.
Insurers often bundle in dental, vision, and hearing, and many advertise zero-dollar premiums.
The catch is what happens when you need real care — the copays, the specialist visits, the out-of-pocket maximum that can legally hit $8,850 for in-network care in 2025.
You keep Original Medicare and buy a supplement that covers most of what Medicare doesn't — deductibles, coinsurance, the 20% that never seems to end.
Premiums are higher and you still need a Part D drug plan, but your costs become predictable.
You see any doctor who takes Medicare, which is most of them.
On Medicare Advantage, you could face daily copays that add up to hundreds or thousands before the plan picks up the rest.
On Plan G, the most popular Medigap option, you pay the Part B deductible — about $257 in 2025 — and then almost everything else is covered.
There's another trap people don't see coming.
Medigap plans are only guaranteed to be sold to you without medical underwriting during your initial enrollment window, usually six months after you turn 65.
After that, insurers in most states can reject you or charge more because of your health history.
Switch to Medicare Advantage and then try to switch back years later with a new diagnosis?
Medicare Advantage isn't automatically the wrong call.
If you're healthy, take few prescriptions, and want low premiums with extras like gym memberships, it can work.
But the plan you pick at 65 may not fit the body you have at 75.
Chronic conditions, cancer treatment, and nursing care are where the cost gap widens and the network restrictions bite.
The smart move is to run your own numbers before you decide.
Add up premiums, deductibles, copays, and the worst-case out-of-pocket maximum for each option.
Check whether your doctors are in the Advantage plan's network.
Look up your drugs on the plan's formulary.
If you can afford the Medigap premium and you expect to need care, the predictability is often worth it.
Some states, like New York and Connecticut, offer more flexibility to switch Medigap plans later.
This isn't about which plan sounds cheaper on a TV ad.
It's about which one you can live with when the bill arrives.
Final Thoughts
Read the fine print, do the math for your own health, and don't let a $0 premium make the decision for you.