Medicare Advantage vs Medigap: The Trade-off Nobody Explains
The decision looks like a premium comparison and is really a decision about future medical underwriting.
At a glance
Figures checked 1 Sep 2026
What to take away
- Medigap is medically underwritten outside your six-month open enrolment window in most states.
- Advantage plans use networks and prior authorisation; original Medicare plus Medigap generally does not.
- Switching back from Advantage to Medigap later may be refused on health grounds.
Original Medicare leaves you exposed to deductibles and a coinsurance share with no annual cap. Two products address that. A Medigap policy sits alongside original Medicare and pays the gaps. A Medicare Advantage plan replaces the delivery of Parts A and B through a private insurer, usually adding drug coverage and extras.
The one-way door
During the six months after your Part B coverage starts, you can buy any Medigap policy sold in your state regardless of health. After that window, most states allow insurers to underwrite you — which means an Advantage enrollee who develops a serious condition may be unable to move to Medigap later.
That asymmetry is the substance of the decision. Choosing Advantage at 65 to save on premiums can quietly close the Medigap door at 72.
Where each fits
- Medigap suits people who travel, split the year between states, or want any Medicare-accepting provider.
- Advantage suits people comfortable within a local network who value the lower premium and bundled extras.
- Either way, check that your specific doctors and drugs are covered annually — Advantage networks and formularies change each year.
Common questions
No. Medigap only works alongside original Medicare and cannot be used with an Advantage plan.
They have real value, but the caps are often low. Price the benefit against what you actually spend rather than the headline.