Medicare's open enrollment window is here, and millions of Americans are staring at the same confusing choice: grab a Medicare Advantage plan with that tempting $0 premium, or pay up for a Medigap supplement.
The ads make Advantage look like a steal.
Medicare Advantage plans often come with networks, prior authorizations, and copays that can climb fast when you actually get sick.
A supplement, also called Medigap, picks up most of what original Medicare leaves behind — but you'll pay a monthly premium that can run $100 to $200 or more depending on your age and state.
The math gets ugly when you run the numbers on a bad year.
On Medicare Advantage, your out-of-pocket costs are capped, but that cap can hit $8,000 or more annually for in-network care.
A Medigap Plan G, by contrast, covers nearly everything after you pay the Part B deductible — roughly $240 in 2025.
The trade-off is real: lower premiums now versus lower bills later.
There's a trap that catches people every year.
If you choose Medicare Advantage when you first enroll and later want to switch to a supplement, most states let insurers charge you more or deny you outright based on your health.
Only a handful of states offer year-round guaranteed switching rights.
Miss that first window, and your cheap plan can become a one-way door.
Medicare Advantage plans usually bundle in Part D, while supplements don't — you'll need a separate drug plan.
That standalone plan runs extra each month, so the true cost gap between the two options is often smaller than the headline premiums suggest.
Run both totals, not just the one on the flyer.
Advantage plans use networks that shift year to year.
Your cardiologist might be in-network this January and out by next.
Supplements work with any provider who takes Medicare, which is most of them.
If keeping your current doctors is non-negotiable, that flexibility has a price tag, and it's usually worth calculating before you decide.
It depends on your health, your budget, and how much uncertainty you can stomach.
Someone with few prescriptions and a tight wallet may do fine on Advantage.
Someone with chronic conditions or a preference for predictable bills often comes out ahead with a supplement.
Neither is universally better, and anyone who tells you otherwise is selling something.
The honest take: treat this like any other insurance decision, not a brand loyalty contest.
Compare total yearly costs, check whether your doctors are covered, and read the out-of-pocket maximums instead of the monthly premium.
Final Thoughts
A few hours with a calculator now can save you thousands when you actually need care.