Every fall, millions of Americans on Medicare face the same confusing fork in the road: stick with original Medicare and add a supplement, or switch to a Medicare Advantage plan with a low monthly premium and extra perks.
The marketing makes Advantage look like a steal.
Original Medicare pays about 80% of covered costs, leaving you on the hook for the rest with no annual cap.
A Medigap supplement picks up most of that leftover, but you pay a monthly premium for the privilege.
Medicare Advantage replaces the whole system with a private plan, often advertising $0 premiums plus dental, vision, and gym memberships.
The catch is what happens when you actually get sick.
Advantage plans use networks, prior authorizations, and copays that can stack up fast during a serious illness.
A 2023 KFF analysis found that a small share of Advantage enrollees rack up thousands in out-of-pocket costs that a Medigap policy would have absorbed.
There's also a trap most people don't learn about until it's too late.
When you first enroll in Medicare, you get a guaranteed right to buy a Medigap policy regardless of health history.
Switch to Advantage and try to come back years later, and insurers in most states can reject you or charge more because of pre-existing conditions.
That one-way door is why financial planners often tell healthier retirees to think hard before trading a supplement for a flashier Advantage pitch.
They can evaporate the moment a diagnosis arrives.
None of this makes Advantage a bad choice for everyone.
If you have low medical needs, a tight budget, and a strong local network, the extra benefits can genuinely help.
The problem is when people pick it based on the commercial, not the coverage.
Consumer advocates say the fix is simple: read the plan's formulary, check whether your doctors are in-network, and ask what the maximum out-of-pocket limit actually is.
Then compare that number to your total Medigap premium for the year.
The decision isn't really about premiums.
It's about how much uncertainty you can stomach, and how much you'd pay if the worst happened.
That math rarely makes it into the 30-second ad.
Our take: the low-premium pitch works because it's easy to sell and hard to audit.
Before you switch, price out a bad year, not just a good one, and check whether your state protects your right to buy a supplement later.
Final Thoughts
The plan that looks free today can be the one that bills you tomorrow.