If you're 65 or older, or helping a parent navigate Medicare, there's a decision sitting in front of you that quietly shapes your finances for years.
It's the difference between a plan that caps your yearly exposure and one that could leave you on the hook for a bill you never saw coming.
The two main paths are Medicare Advantage (Part C) and Medicare Supplement plans, often called Medigap.
And the gap between them shows up in your wallet, usually at the worst possible time.
Medicare Advantage plans work like an HMO or PPO.
You typically get a low or $0 monthly premium, plus extras like dental, vision, and hearing.
But you stay inside a network, and you often need referrals or prior authorization.
There's also an annual out-of-pocket maximum, which in 2025 sits at $9,350 for in-network care on many plans, according to federal limits.
That's your worst-case number, and it resets every January.
You pay a monthly premium, and in exchange, the plan covers most or all of the gaps Original Medicare leaves behind, like the 20% coinsurance on doctor visits and hospital costs.
You see any provider who accepts Medicare.
And there's no annual reset on your exposure because the coverage is predictable.
A single hospital stay or a cancer diagnosis can push your Advantage out-of-pocket costs toward that multi-thousand-dollar ceiling.
With Medigap, that same event might cost you a few hundred dollars.
The trade-off is the premium, which can run $100 to $250 a month or more depending on your age, gender, and state.
The catch that trips people up: Medigap has enrollment windows.
If you miss your one-time Medigap Open Enrollment Period, which starts the month you turn 65 and enroll in Part B, insurers in most states can charge you more or deny you outright based on health history.
Advantage plans, by contrast, let you switch during the annual Open Enrollment Period each fall.
That asymmetry is why financial planners often tell healthier 65-year-olds to consider Medigap first.
You can always move to Advantage later in many cases.
If you travel, snowbird, or want access to a specific specialist at a major hospital, Advantage networks can get restrictive.
Medigap follows you anywhere in the country that takes Medicare.
If you have limited income and qualify for subsidies, an Advantage plan's extras and low premium can stretch a budget further.
If you can afford the monthly cost and want to cap your downside, Medigap tends to win on predictability.
Check your current plan's drug coverage too, since Part D formularies change every year.
A medication you take could jump tiers or drop off entirely, and that alone can flip the math.
Medicare Open Enrollment runs through December 7, and Advantage plan changes take effect January 1.
Missing it means waiting another year. **Our take:** This isn't a set-it-and-forget-it decision, and the stakes are too high to guess.
Final Thoughts
Run your actual doctors, prescriptions, and travel plans against both options before the deadline, because the cheapest premium today can become the most expensive choice tomorrow.