If you're turning 65 this year, you're about to make one of the most expensive decisions of your retirement — and most people rush it in a single afternoon.
The two main paths are Medicare Advantage (Part C) and Medicare Supplement plans, often called Medigap.
They behave nothing alike when a hospital bill lands on your kitchen table.
Medicare Advantage works like an HMO or PPO you may already know from employer coverage.
You stay in a network, pay copays for visits, and often get extras like dental, vision, and gym memberships folded in.
The trade-off: you generally can't pair it with Medigap, and you may face prior authorizations for care your doctor says you need.
You pay a private insurer a monthly premium on top of your Part B premium, and in exchange, the plan picks up most of what original Medicare doesn't — coinsurance, copays, and in many cases, the deductible.
You see any provider in the country who accepts Medicare.
The catch that trips people up is the enrollment window.
When you first sign up for Part B, you get a six-month Medigap open enrollment period.
During that window, insurers can't turn you down or charge you more because of your health history.
Miss it, and in most states you can be denied coverage or quoted a price based on your conditions.
That single rule is why financial planners tell healthy 65-year-olds to at least price a Medigap plan before defaulting to Advantage.
A cancer diagnosis or a bad fall at 68 can lock you out of the cheaper supplement market for good.
Medicare Advantage, meanwhile, has its own trap.
You can switch back to original Medicare during the annual enrollment window, but getting a Medigap policy after you've been on Advantage often requires medical underwriting.
Some states, including New York and Connecticut, offer more flexibility, but most don't.
Advantage plans often show a $0 monthly premium, which looks unbeatable next to a Medigap premium that might run $150 to $250 a month.
But the Advantage plan's out-of-pocket maximum can hit $8,850 in-network in 2025, and higher if you go out of network.
A rough year with surgery and specialists can wipe out the savings fast.
Medigap's predictability is its selling point.
A hospital stay doesn't come with a surprise bill, and you don't need a referral to see a specialist.
It depends on three things: your health, your budget, and how much uncertainty you can stomach.
If you have chronic conditions, travel a lot, or want zero network headaches, Medigap is usually the safer bet.
If you're healthy, want low upfront costs, and don't mind staying in a network, Advantage can work well — especially if you use the dental and vision perks.
Every fall, your mailbox fills with celebrity-fronted commercials promising free rides to appointments and grocery allowances.
Those extras are real, but they're not the reason to pick a plan.
Look at the formulary, the network, and the star ratings instead.
My take: treat this like buying a house, not picking a phone plan.
Get help from your State Health Insurance Assistance Program, which offers free counseling, and ask what happens if you get sick — not what happens if you stay healthy.
Final Thoughts
The wrong choice can follow you for a decade.