Medicare
Medicare Advantage vs. Medigap: Why the Choice Can Be Hard to Undo
One road has low premiums and a network, the other has high premiums and almost no bills, and the rules make it far easier to move in one direction than the other.
Margaret Linwood
Updated Sep 22, 2026 · 11 min read
Most Medicare decisions come with a do-over. Pick a drug plan you don't like and you can change it next fall. Join a Medicare Advantage plan with the wrong network and you can move to another one between October 15 and December 7, or again between January 1 and March 31. The door reopens every year.
One decision doesn't work that way. When you first go on Medicare, you choose between two roads. On one, you join a private Medicare Advantage plan. On the other, you stay in Original Medicare and buy a Medigap policy, also called Medicare Supplement Insurance, to pay the bills Medicare leaves behind. You can go from Medigap to Medicare Advantage in any fall enrollment period with one phone call.
Going the other way is a different story. Outside a few protected situations, federal law doesn't require a Medigap insurer to sell you a policy, and in most states the company can ask about your health, check your prescription history, and then charge you more or turn you down. KFF, the health policy research group, estimated that 9 in 10 Medicare Advantage enrollees 65 and older, about 22.4 million people as of 2022, had no guaranteed right to buy Medigap once their first-year trial period was over.
So the choice that feels routine at 65, often made in a few minutes because one option shows a $0 premium, can turn close to permanent a decade later. That's usually when health has changed and the other road has started to look better. Bad timing, built in.
None of this makes Medicare Advantage the wrong choice. It means you should pick it knowing which way the door swings.
Two roads, side by side
Both roads start in the same place. You have Part A and Part B, and you pay the Part B premium, $202.90 a month in 2026.
Medicare Advantage replaces how you get that coverage. A private insurer runs it, usually with a network of doctors and hospitals and its own rules about approvals. More than half of eligible people are on this road: 35.2 million in 2026, or 55%, by KFF's count. Two-thirds of the plans with drug coverage charge no premium of their own, and nearly all include some dental, vision and hearing benefits.
Original Medicare with Medigap keeps the government as your insurer. Medicare pays its share and the Medigap policy pays most or all of the rest. You can see any provider in the country that takes Medicare, and you rarely need permission first. You buy a separate Part D plan for prescriptions. About 12.5 million people had a Medigap policy in 2023, according to KFF.
The premium figures below are KFF national averages. Your local prices will differ.
| Medicare Advantage | Original Medicare + Medigap Plan G + Part D |
|---|
| Monthly premiums beyond Part B | Often $0 | About $164 for Plan G (2023 average) plus about $36 for a drug plan (2026 average) |
| Medical costs in a healthy year | Copays per visit | The Part B deductible, $283 in 2026 |
| Medical costs in a bad year | Up to the plan's out-of-pocket maximum, which federal rules capped at $9,250 in-network for 2026 | The same $283. Plan G pays the rest of covered Part A and B costs |
| Doctors and hospitals | The plan's network | Any that accept Medicare |
| Approval before care | Common for certain services | Rare |
| Dental, vision, hearing | Usually included, with limits | Not included |
| Switching later | Any fall, to another Medicare Advantage plan | Medigap insurers can ask health questions in most states |
The trade's right there in the numbers. In this example the Medigap road costs about $200 a month more in premiums, around $2,400 a year, doctor visits or not. The Medicare Advantage road costs little up front and more when you use it. Pay now or pay later.
KFF estimated that 22.4 million Medicare Advantage enrollees 65 and older, 9 in 10, had no guaranteed right to a Medigap policy if they wanted to switch back.
So why would anyone want to switch back?
People rarely leave a $0 plan while they're healthy. The wish tends to show up with a serious diagnosis, a specialist who's out of network, a string of prior authorization requests, or a move across state lines to be closer to family. Those are the same moments when a Medigap application is most likely to be priced up or declined.
KFF's analysis lists conditions that can lead to a denial, among them diabetes with complications, congestive heart disease, cancer and asthma. Each company sets its own rules, though, and a person turned down by one insurer may be accepted by another. Some conditions lead to a higher price rather than a flat no.
There are exceptions, and a few of them are wider than people expect. If you're choosing for the first time, or you're already in Medicare Advantage and want to know whether the door's still open, read the next part slowly.
