A handful of states give Medicare Supplement policyholders something federal law does not: a guaranteed yearly window, tied to their birthday, to switch to another Medigap plan without answering a single health question. Outside that window, and in most of the country, an insurer can review an applicant’s medical history and charge more or refuse coverage when someone tries to change plans. The birthday rule turns what is normally a gamble for retirees with health conditions into a routine, once-a-year chance to shop for a cheaper policy.
How the birthday rule sidesteps medical underwriting
Under federal law, a retiree gets one guaranteed shot at any Medigap plan when first enrolling in Medicare Part B at 65, a stretch called the Medigap open enrollment period. After those six months close, insurers in most states may use medical underwriting on anyone trying to switch, meaning they can weigh existing conditions and deny an application or raise the premium. Medicare’s own Medigap guidance makes clear that once the initial window passes, guaranteed acceptance becomes the exception rather than the rule.
The birthday rule is a state-created exception to that underwriting. In states that have adopted it, insurers must let existing Medigap policyholders move to a comparable or lower-benefit plan during a set number of days around their birthday each year, without health screening. Because the switch is guaranteed regardless of medical history, a retiree who developed a serious condition after age 65 can still change carriers to chase a lower premium, something that would ordinarily be impossible without passing underwriting.
The financial stakes sit in the premium. Two insurers can sell the identical standardized Medigap plan — the benefits of Plan G or Plan N are set by rule and do not vary from one company to the next — yet charge very different monthly rates for it, and those rates tend to climb with age. The birthday rule lets a policyholder locked into a pricey plan move to a cheaper carrier offering the same coverage, potentially saving hundreds of dollars a year, without the risk of being turned away.
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Which states offer the window, and how long it lasts
The rule is not federal, so it exists only where a state has written it into law, and the list has grown. As of 2026, roughly a dozen and a half states offer some version, including California, Oregon, Nevada, Idaho, Illinois, Louisiana, Maryland, Kentucky, and Washington, with Delaware and Indiana adding rules that took effect at the start of 2026. Each state sets its own terms, so the protection a retiree gets depends heavily on where they live.
The length of the window varies from state to state, generally running between 30 and roughly 60 days and anchored to the policyholder’s birthday. California, for example, opens a 60-day window that begins on the birthday, as an overview of the state birthday rules details. Some states start the clock on the birthday itself while others begin it earlier, so missing the exact dates can mean waiting a full year for the next chance.
The roster keeps shifting as more states act. West Virginia’s version took effect in mid-2026, and New Mexico enacted a rule scheduled to begin in 2027, signs that the protection is spreading even though it remains a minority of states. For retirees, that churn is a reason to recheck the current rules each year rather than relying on an old list, since a state without the rule today could adopt one before the next birthday comes around.
The equal-or-lesser-benefit catch
The birthday rule almost never allows an upgrade. In nearly every state that offers it, a policyholder may switch only to a plan with equal or lesser benefits, which means someone on Plan N generally cannot use the window to jump to the more generous Plan G without facing underwriting. The guaranteed-acceptance protection is designed to help retirees lower costs on comparable coverage, not to add benefits they did not previously carry.
That limit shapes the strategy. A retiree using the window is typically moving sideways to the same standardized plan at a cheaper carrier, or stepping down to a plan with a slightly higher share of costs in exchange for a lower premium. Medicare’s comparison of standardized Medigap benefits shows exactly which plans sit above or below one another, which determines what a birthday-rule switch can and cannot reach.
For the retirees who happen to live in a birthday-rule state, the mechanism is one of the few reliable ways to escape a rising Medigap premium after the initial enrollment window has closed. Its value depends entirely on geography and on calendar discipline: the protection is real, but it is narrow, time-boxed, and capped at equal-or-lesser coverage. Anyone counting on it should confirm their own state’s exact window and benefit rules well before the birthday arrives, because a missed date resets the wait by a full year.
This article was produced with AI assistance and reviewed against primary sources by The Money Overview editorial team.
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