Every fall, millions of Americans on Medicare face the same fork in the road: stick with Original Medicare plus a supplement plan, or switch to a Medicare Advantage plan with a low monthly premium and extra perks.
The wrong pick can leave you on the hook for thousands of dollars in medical bills you never saw coming.
The pitch for Medicare Advantage is hard to ignore.
Many plans advertise $0 monthly premiums, dental, vision, hearing aids, and gym memberships bundled together.
But those extras often come with trade-offs buried in the fine print.
Advantage plans use networks, prior authorizations, and copays that can add up fast if you get seriously ill.
Medigap, also called a Medicare supplement, works differently.
You pay a private insurer a monthly premium on top of your Part B premium, and in return the plan covers most or all of the gaps Original Medicare leaves behind.
There are no networks for doctors who accept Medicare, and no prior authorization for covered care.
A Medigap Plan G can run $120 to $200 or more per month depending on your age, gender, and zip code.
The math gets real when you actually use your coverage.
With Medicare Advantage, your out-of-pocket costs are capped each year, but that cap can be $4,000 to $8,000 or higher for in-network care.
Go out of network and you could pay more.
With Medigap Plan G, once you cover the Part B deductible, which is $257 in 2026, the plan picks up nearly everything else.
If you choose Medicare Advantage when you first enroll and later want to switch to Medigap, you may have to pass medical underwriting in most states.
That means an insurer can charge you more, or reject you outright, because of a pre-existing condition like diabetes, heart disease, or cancer.
In a handful of states, like New York and Connecticut, you can switch more easily, but most Americans don't have that protection.
If you start with Medigap and later want Medicare Advantage, you can usually switch during the annual enrollment window without answering health questions.
It's one reason financial planners often tell healthier clients to grab Medigap early while they still can.
If you have a chronic condition, see specialists often, or travel a lot, Medigap's higher monthly premium can pay for itself quickly.
If you're healthy, live on a tight budget, and mostly need routine care, a Medicare Advantage plan with a low premium might stretch your dollars further.
The key is to read the plan's formulary, provider list, and out-of-pocket maximum before you sign up, not after.
There's no universal winner here, and anyone who tells you otherwise is selling something.
Run your own numbers, check whether your doctors are in network, and look at what a bad year would actually cost you.
Final Thoughts
The plan that looks cheapest in October can be the most expensive one by March.