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 steered toward the wrong answer without even realizing it.
The two main paths are Medicare Advantage (Part C), where private insurers bundle your coverage, and Original Medicare paired with a Medigap supplement.
Many plans advertise $0 monthly premiums, plus dental, vision, and gym memberships.
But the fine print hides the real math, and it can hit you hard the year your health changes.
Here's the gap nobody mentions at the enrollment seminar.
Advantage plans cap your out-of-pocket costs, but those caps run as high as $9,350 in-network for 2025 — and Medicare Advantage enrollees often face network restrictions, prior authorizations, and referrals just to see a specialist.
A 2023 KFF analysis found that nearly half of Advantage prior authorization denials were later overturned on appeal.
That means patients were initially told no for care they were actually owed.
You pay a monthly premium — often $100 to $200 depending on your state and plan letter — on top of the standard Part B premium.
In exchange, most plans cover nearly all of the 20% of costs Original Medicare leaves behind.
You see any provider in the country who accepts Medicare.
For snowbirds and anyone with a serious diagnosis, that flexibility is worth real money.
If you choose Medicare Advantage when you first enroll and switch to Medigap later, most states let insurers medically underwrite you.
That means they can reject you or charge more because of your health history.
A cancer diagnosis, diabetes, or even a treated back condition can lock you out of the supplement you suddenly need.
Only a handful of states — including New York and Connecticut — offer year-round guaranteed acceptance.
If you can afford the Medigap premium and want to keep your doctors, many financial planners say to start there.
If cost is the barrier and you're generally healthy, Advantage can work — but go in knowing you're trading flexibility for a lower monthly bill, and that trade can reverse overnight.
One more trap: Advantage plans' extra benefits like dental and vision often carry their own annual caps, sometimes just $1,000 to $2,000.
A single crown or pair of glasses can eat most of that.
Read the summary of benefits, not the sales brochure.
The bottom line is that this isn't really a "which is cheaper" question.
It's a question of how much risk you're willing to carry and whether you can still switch later if your health turns.
The wrong pick in your mid-60s can cost you five figures in your 70s, when changing your mind may no longer be an option.
My take: treat the Medigap deadline like a financial fire drill.
Talk to a licensed broker who sells both products, not a captive agent paid to push one.
Final Thoughts
The hour you spend comparing plans at 65 could be the highest-paid hour of your retirement.