Every fall, roughly 60 million Medicare enrollees get buried in glossy mailers promising "$0 premium" plans, dental perks, and grocery cards.
What those mailers rarely explain is that the two main paths — Medicare Advantage (Part C) and Medicare Supplement (Medigap) — work in completely opposite ways.
One trades lower upfront costs for tighter networks and prior authorizations.
The other costs more monthly but lets you see almost any doctor who takes Medicare.
It can mean thousands of dollars out of pocket in a bad year.
Medicare Advantage is the privatized version: the government pays an insurance company a set amount per member, and that company manages your care.
Premiums can be $0 beyond your Part B payment, and many plans bundle in drug coverage, dental, vision, and gym memberships.
The catch is that the insurer controls the network, the referrals, and increasingly the approval process.
A 2023 KFF analysis found that Medicare Advantage plans denied about 3.4 million prior authorization requests in a single year — roughly 6 percent of them.
You keep original Medicare, and a private supplement policy picks up most of the copays and coinsurance that Medicare leaves behind.
You can generally see any provider nationwide who accepts Medicare, with no referrals and no prior authorization for covered services.
The tradeoff is cost: a Plan G policy can run $120 to $200 a month depending on your age, state, and health history, on top of the standard Part B premium — about $185 a month in 2025.
Here's the trap almost nobody mentions at the kitchen table.
Medigap insurers in most states can medically underwrite you after your initial enrollment window.
If you pick Medicare Advantage at 65 because it's cheap, then get diagnosed with something serious at 70, switching to Medigap may be either impossible or priced out of reach.
Your one guaranteed shot at Medigap without health questions is the six-month window that starts when you first enroll in Part B.
Medicare Advantage has its own timing risk.
You can switch plans or drop back to original Medicare during the annual Open Enrollment period, October 15 to December 7.
But dropping to original Medicare without a supplement leaves you exposed to Medicare's 20 percent coinsurance with no annual cap.
A single extended hospital stay or cancer treatment can produce bills in the tens of thousands.
The insurance companies and the brokers paid commissions to steer you.
Medicare Advantage enrollment crossed 50 percent of all eligible beneficiaries in 2023, and plans spend heavily on marketing because each new member is recurring revenue.
That doesn't make the plans bad — for healthy people with low drug costs and a tight budget, they often work fine.
It just means the sales pitch is not neutral advice.
The practical move: price both options before you turn 65, not after.
Add up premiums plus worst-case out-of-pocket maximums for each.
Check whether your doctors and hospitals are actually in the Advantage plan's network — not just listed, but accepting new patients.
And if you have any chronic condition or family history that worries you, weigh what losing the Medigap guarantee would cost later.
My take: the system is designed to reward whoever signs you up, not whoever keeps you covered for 25 years.
Treat the $0 premium flyer as a marketing document, not a financial plan.
Final Thoughts
The cheapest option today is often the most expensive one at 75.