If you are turning 65 this year, you have probably been buried in mailers promising free dental, free groceries, and a $0 monthly premium.
Those ads are selling Medicare Advantage, and they almost never mention what happens when you actually get sick.
The alternative is a Medicare Supplement plan, often called Medigap.
It works very differently, and the gap between the two can add up to thousands of dollars a year once real medical bills start arriving.
Original Medicare pays about 80% of covered costs, and you cover the rest, with no yearly cap on that 20%.
A Medigap policy picks up most or all of that leftover share, so a hospital stay or a round of cancer treatment does not wreck your budget.
Medicare Advantage replaces Original Medicare with a private plan, usually through an insurer like UnitedHealthcare or Humana.
You often pay a low or zero premium, and many plans throw in extras like vision, dental, and a gym membership.
The trade-off is networks, prior authorizations, and copays that can pile up fast.
That extra spending has a ceiling, but it is a high one.
In 2024, Advantage plans could charge up to $8,850 in in-network out-of-pocket costs for covered services, and up to $13,300 if you use out-of-network care.
Medigap has no such limit because it is filling in behind Original Medicare instead.
Depending on your state, age, and plan letter, you might pay $100 to $300 or more per month on top of your Part B premium.
That is real money, and it is the main reason people walk away.
But there is a window that matters more than the price.
When you first enroll in Medicare Part B at 65, you get a six-month Medigap open enrollment period.
During that time, insurers cannot reject you or charge you more because of your health history.
In most states, an insurer can look at your diabetes, your heart condition, or your past cancer treatment and either charge you a higher rate or turn you down entirely.
A few states, including New York and Connecticut, have rules that make switching easier year-round, but most do not.
This is why the decision is less about which plan sounds better on TV and more about your health and your savings.
If you have a chronic condition, take expensive drugs, or travel a lot, Medigap plus a standalone Part D drug plan often costs more upfront but far less when something goes wrong.
If you are healthy, take few prescriptions, and want to keep monthly costs low, Advantage can work well.
Just read the plan's drug list, check whether your doctors are in network, and understand that the plan can change its coverage every year.
One more thing people miss: you can be disenrolled from an Advantage plan if you move out of its service area or if the plan leaves your county.
Medigap does not work that way, and it follows you across most states.
The closing thought: this is not a contest between good and evil, it is a bet on your future health.
Final Thoughts
Whichever way you lean, make the call during that first six-month window, because that is the one time the system lets you choose without answering for your medical history.