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Buying a Medigap plan is easy the first time. Your six-month open enrollment period, which starts when you turn 65 and enroll in Part B, gives you a federal guarantee: insurers must sell you any plan they offer, cannot charge more because of your health, and cannot make you wait for pre-existing conditions beyond a limited period. After that window closes, switching plans gets harder, but not impossible.
Why switching is restricted
Outside your initial open enrollment, Medigap insurers in most states can use medical underwriting. That means health questions, and they can deny you or charge higher premiums based on the answers. A plan that would have cost you the standard rate at 65 can be unavailable or much more expensive at 72 after a diagnosis. This is the single most misunderstood part of Medigap, and it is why the plan you pick at 65 matters more than people think.
Guaranteed issue rights: when underwriting does not apply
Federal law carves out specific situations where you can switch or buy Medigap without underwriting. These are called guaranteed issue rights, and they cover the cases where your coverage disappeared through no fault of yours.
The trial right is the most useful one. If you joined a Medicare Advantage plan when you first became eligible and decide within the first 12 months that you want Original Medicare instead, you can buy any Medigap plan sold in your state with no underwriting. There is a second trial right if you dropped Medigap for Advantage and want your old plan back within a year.
Other triggers include your Medigap insurer going bankrupt, your Medicare Advantage plan leaving your area or shutting down, moving out of your plan’s service area, or losing employer or union coverage that was paying after Medicare. Each trigger comes with its own deadline, usually 63 days from when the old coverage ends, so act quickly when one applies.
States that make switching easier
A handful of states go beyond federal rules and let you switch Medigap plans without underwriting on a regular basis. California and Oregon have birthday rules that give you a window around your birthday each year to switch to an equal or lesser plan. Several other states have continuous or annual guaranteed issue provisions of their own. If you live in one of these states, your switching options are much wider than the federal minimum, and it is worth confirming the current rules with your state insurance department, since they change.
What to do before you try to switch
First, do not cancel your current plan until the new one is approved and active. A gap in Medigap coverage is exactly what the guaranteed issue deadlines punish. Second, apply early enough that underwriting, if it applies, finishes before you need the new plan to start. Third, compare the same plan letter across insurers, since benefits are standardized and price is the main variable.
If you are switching because your premium keeps climbing, get quotes for the same letter from at least three insurers before assuming you need a lesser plan. Premium increases are often insurer-specific, and the same Plan G can cost meaningfully different amounts from different companies in the same zip code.
If you are still choosing between the Medigap path and Medicare Advantage, our Advantage vs Medigap comparison covers the structural tradeoff. And if you have not yet bought your first supplement, the timing rules in the Medicare parts guide explain when your open enrollment window opens.
