If you're turning 65 or already on Medicare, you've probably been buried in mailers promising free dental, gym memberships, and grocery cards.
Those glossy flyers almost always pitch Medicare Advantage.
What they don't mention is the trade-off hiding in the fine print.
Medicare Advantage (Part C) is run by private insurers who contract with the government.
You often pay a $0 premium on top of your Part B, and you get extras like vision and hearing.
The catch: you stay inside a network, and you generally need referrals or prior approval for expensive care.
Original Medicare plus a Medigap supplement works differently.
You pay a monthly premium, but you can see almost any doctor in the country who accepts Medicare, with no networks and no prior authorization for most services.
A Medigap Plan G for a 65-year-old can run roughly $100 to $160 a month depending on your state, and it climbs with age.
Advantage plans often advertise $0 premiums because the government pays insurers a set amount per member.
That model works fine when you're healthy and rarely use care.
It gets expensive fast when you actually get sick.
Advantage plans cap your out-of-pocket costs each year, but those caps can hit $8,000 or more for in-network care, and higher if you go out of network.
A supplement plan typically leaves you with a predictable, small bill after Medicare pays its share.
For someone facing cancer treatment or a major surgery, that difference can be tens of thousands of dollars in a single year.
In most states, Medigap insurers can ask about your health once you're past your initial enrollment window.
If you start with Advantage and develop a condition, you may be denied a supplement later.
A handful of states, including New York and Connecticut, let you switch year-round regardless of health.
First, add up your real costs, not just the premium.
Look at your prescriptions on each plan's formulary, check whether your doctors are in network, and read the out-of-pocket maximum.
Second, think about your health trajectory, not just this year.
Third, if you can afford a supplement during your one guaranteed window, many financial advisors argue it's worth locking in.
The honest answer is that neither option wins for everyone.
If you're healthy, want low premiums, and can live with a network, Advantage can save you money.
If you want freedom to see specialists and predictable costs, a supplement usually wins.
The mistake is choosing based on a mailer instead of your own math.
Call your doctors, price your drugs, and run the numbers.
Final Thoughts
The plan that looks cheapest in January is often the one that hurts most in July.