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 and a Medicare Supplement plan can swing your annual health care costs by $5,000 or more, depending on how often you see doctors.
Medicare Advantage (Part C) replaces Original Medicare.
You get coverage through a private insurer, often with $0 monthly premiums, plus extras like dental, vision, and gym memberships.
Medicare Supplement plans (Medigap) sit on top of Original Medicare and pick up the costs it leaves behind.
You pay a monthly premium — often $100 to $200 or more — but you can see any doctor in the country who accepts Medicare.
The trap with Advantage plans is the fine print.
Low premiums come with networks, prior authorizations, and copays that can add up fast.
A 2024 KFF analysis found that Medicare Advantage enrollees faced prior authorization requirements on 99% of their drug coverage and a growing share of medical services.
When a claim gets denied, you or your doctor have to fight it.
Medigap buyers get something Advantage enrollees don't: predictability.
Once you're enrolled, Plan G or Plan N covers most of what Medicare doesn't, and you can budget a fixed monthly cost.
You have a one-time, six-month Medigap open enrollment window when you first sign up for Part B at 65.
After that, insurers in most states can charge you more or deny you outright based on your health history.
That rules out switching later for many people.
If you pick Advantage at 65 and develop a chronic condition, moving to Medigap may be financially painful — or impossible.
A few states, including New York and Connecticut, offer year-round guaranteed enrollment, but most don't.
A 2023 study published in JAMA found that Medicare Advantage plans cost taxpayers roughly 7% more per enrollee than traditional Medicare, despite the marketing pitch that they save the system money.
For your household budget, what matters is your total out-of-pocket exposure — and Advantage plans cap it, but often at $7,000 to $8,500 per year for in-network care.
Ask yourself three questions before you decide.
How often do you see specialists, and are they in the plan's network?
Do you travel or split time between states?
And can you comfortably absorb a $150 monthly Medigap premium for the next 20 years?
Your answers matter more than any broker's sales pitch.
The Annual Enrollment Period runs October 15 through December 7, and Advantage open enrollment runs January 1 through March 31.
Miss those windows and your options shrink.
One last warning: if you enroll in an Advantage plan during your initial window, you can usually switch to Medigap within 12 months under a trial right — but only once, and the rules are strict.
Document everything and confirm with your state's Senior Health Insurance Information Program (SHIP) before you sign. **Our take:** The right answer depends on your health and your tolerance for uncertainty, not on which plan has the flashiest ad during the World Series.
If you can afford the premium and want to keep your doctors, buying Medigap at 65 is often the cheapest decision you'll ever make.
Final Thoughts
If cash flow is tight now and you're comfortable with network rules, Advantage can work — just go in with your eyes open, because the door to switch may close behind you.