Open enrollment runs through December 7, and millions of Americans on Medicare are staring at the same fork in the road.
One path is Medicare Advantage, the all-in-one private plan that often advertises $0 premiums.
The other is Original Medicare paired with a Medigap supplement, which carries a monthly bill but fewer surprises.
The gap between these two options can run into thousands of dollars a year, and the wrong pick is hard to undo.
Medicare Advantage works like an HMO or PPO.
You get hospital, medical, and usually drug coverage through one private insurer, often with extras like dental, vision, and gym memberships.
Stay in-network and costs stay predictable.
Go out, and you can be stuck with the bill.
Plans also cap total yearly spending, but that cap can sit as high as $8,850 for in-network care in 2025, and higher if you use out-of-network providers.
You keep Original Medicare and buy a supplement that covers most of the gaps, like the 20% coinsurance on doctor visits and hospital stays.
There are no networks, so you can see any provider nationwide who accepts Medicare.
The catch is the premium, which varies by state, age, and plan letter.
A Plan G for a 65-year-old can run $100 to $200 a month, and it climbs with age.
The math gets interesting when you compare total exposure.
A Medicare Advantage enrollee might pay little in premiums but face copays for every specialist visit, hospital stay, and scan.
A Medigap enrollee pays a steady premium but has near-zero cost-sharing after the deductible.
For someone with a chronic condition or a cancer diagnosis, the supplement often wins on total cost.
For a healthy 65-year-old who rarely sees a doctor, Advantage can look cheaper on paper.
With rare exceptions, you can only buy a Medigap policy without medical underwriting during your six-month Medigap Open Enrollment Period, which starts the month you turn 65 and enroll in Part B.
After that window closes, an insurer can reject you or charge more because of pre-existing conditions.
Switch from Advantage to Medigap later, and you may be locked out entirely.
Medicare Advantage is easy to enter and hard to leave if your health changes.
Medigap is harder to enter but far more flexible once you are in.
Advantage plans also change their networks and formularies every year, so the plan you picked in January may look different next January.
Advantage plans usually bundle Part D, while Medigap does not, so you need a standalone drug plan.
Those premiums and formularies shift annually too.
Comparing a $0 Advantage premium against a $150 Medigap premium plus a $40 drug plan is not apples to apples until you factor in copays, deductibles, and out-of-pocket maximums.
For anyone with ongoing medical needs or a preference for seeing specialists without referrals, the supplement route tends to offer more breathing room.
For budget-focused enrollees in good health, Advantage can keep monthly costs near zero.
The mistake is deciding on premium alone, because the biggest bills arrive when you actually get sick.
The takeaway: treat this as a total-cost decision, not a monthly-bill decision.
If you can afford the premium and qualify during your initial window, locking in a Medigap policy buys you options you cannot easily buy later.
Final Thoughts
If cash flow is tight and your health is stable, Advantage can work, but read the out-of-pocket cap and network rules before you sign.