If you're turning 65 this year, you're about to face one of the most expensive decisions of your retirement — and most people get it wrong.
The choice between Medicare Advantage (Part C) and a Medicare Supplement (Medigap) plan looks like a simple comparison.
The two paths lead to wildly different medical bills, doctor networks, and out-of-pocket maximums.
Pick the wrong one and you could be on the hook for thousands of dollars you never planned for.
Here's the part that trips people up: Original Medicare (Parts A and B) covers only about 80% of most medical costs.
A single extended hospital stay or cancer treatment can leave you owing tens of thousands.
Both Medicare Advantage and Medigap exist to fill that gap — but they do it in opposite ways.
Medicare Advantage works more like an HMO or PPO through a private insurer.
You often get extra perks like dental, vision, and gym memberships, and many plans carry a $0 monthly premium beyond your Part B payment.
The trade-off: you're locked into a network.
And while plans cap annual out-of-pocket costs, that cap can run $8,000 or more in 2025 — real money for someone on a fixed income.
You pay a monthly premium — often $100 to $200 or more depending on your state and age — but in exchange, the plan picks up most or all of that dreaded 20% coinsurance.
You can see any doctor nationwide who accepts Medicare.
For snowbirds and anyone with ongoing health issues, that flexibility is worth serious money.
The catch that nobody warns you about: Medigap has a one-time open enrollment window.
You get six months starting the month you're 65 and enrolled in Part B.
During that window, insurers can't turn you down or charge you more for pre-existing conditions.
Miss it, and you may be denied coverage or charged a higher rate for the rest of your life.
Medicare Advantage, by contrast, lets you switch plans every year during open enrollment — but switching back to Medigap later can be brutally hard.
It depends on three things: your health, your budget, and how much uncertainty you can stomach.
If you're generally healthy and want low upfront costs, Medicare Advantage can work well.
If you have chronic conditions, travel, or simply hate surprise bills, Medigap often pays off over time — even with the higher premium.
One more trap: those flashy Medicare Advantage ads promising "extra benefits" rarely mention the prior authorizations that can delay or deny care.
A 2023 federal report found some plans denied requests that should have been approved.
Our take: treat this like the financial decision it is, not a quick checkbox at the pharmacy counter.
Final Thoughts
Talk to a licensed broker who isn't paid to push one product, compare total yearly costs — not just the monthly premium — and lock in your decision before that six-month Medigap window closes for good.