Turning 65 begins a six-month enrollment window that closes permanently for most applicants. During that half-year, private insurers must sell a new Medicare enrollee any Medigap policy they offer in that state, at their best available rate, without asking a single health question. After the window closes, in most of the country, the same insurers can look at an applicant’s medical history and legally say no.
The federal Medigap Open Enrollment Period is a one-time, six-month window that begins the first month a person is both 65 or older and enrolled in Medicare Part B, according to the Medicare.gov guidance and the National Council on Aging. During those six months, coverage is guaranteed issue. Outside of it, insurers in most states can use medical underwriting, meaning they can deny an application, exclude a pre-existing condition, or charge a higher premium.
Why the Window Matters at 65
Medigap is the private supplemental coverage that fills the deductibles, copays, and 20% coinsurance that Original Medicare leaves behind. Roughly 13.6 million Americans hold a Medigap policy, per the KFF Medigap enrollment tracker, and in 2023, Medigap covered about 20% of all Medicare beneficiaries and 43% of those in traditional Medicare. For that group, the six-month window at age 65 was the only chance most had to pick a plan without a health interview.
The standard Medicare Part B premium in 2026 is $202.90 per month, and the Part B annual deductible is $283, per NCOA’s 2026 cost breakdown. On top of that, the average Medigap premium runs around $189 a month at age 65 and rises to roughly $238 by age 75, according to MoneyGeek. A denial after 65 can lock a beneficiary out of the product entirely, not simply raise the price of entry.
What Underwriting Actually Looks Like
Once the six-month window closes, insurers in most states apply the same tools any life or health carrier uses. Applications ask about diabetes, heart disease, cancer history, current medications, and recent hospitalizations. A single answer can move an applicant from “accepted at standard rates” to “rated up” or “declined.” That is the ordinary practice in health insurance underwriting, and it is why financial commentators, including Clark Howard on his podcast, routinely tell listeners approaching Medicare age to pay very close attention to what is considered to be a covered medical reason and how pre-existing conditions are treated in any related coverage decision.
Federal law carves out a handful of limited “guaranteed issue” situations later in life, such as losing employer coverage or a Medicare Advantage plan leaving a service area. Those are narrow exceptions that apply only in narrow circumstances and leave the month-six deadline in place.
Four States Where the Rules Are Different
State law can be more generous than the federal floor. According to KFF’s analysis of Medigap availability for beneficiaries with pre-existing conditions and Medicare consumer resources:
- Connecticut requires continuous guaranteed issue for Medigap year-round.
- New York also requires continuous guaranteed issue year-round.
- Massachusetts mandates an annual guaranteed-issue period.
- Maine offers an annual guaranteed issue window for Plan A.
Everyone else lives under the federal rule. Missing the birthday window in the other 46 states puts the beneficiary at the mercy of the insurer’s medical questionnaire.
The Money Behind the Decision
The stakes rise because retirement income is fixed. The 2026 Social Security COLA is 2.8%, per the Social Security Administration’s June 2026 update. Medigap premium inflation has often outpaced that adjustment. A retiree denied a preferred Medigap plan at 68 can end up on a Medicare Advantage plan with narrower networks, or on Original Medicare with no cap on out-of-pocket costs. That is the practical consequence of a paperwork deadline that arrives quietly in the mail with a Part B card.
What to Do With the Window
Three considerations shape how the window is typically used:
- Enroll in Part B on time. The Medigap window does not open until Part B is active, and delaying Part B without qualifying employer coverage also triggers a lifetime late enrollment penalty.
- Compare Medigap plans in the state before the end of June. Plan letters (A, G, N, and others) are standardized, while premiums vary by carrier, and the initial rate locks in the underwriting-free entry point.
- Check state rules. Residents of Connecticut, New York, Massachusetts, and Maine have more flexibility than the federal minimum, and moving between states can change the calculus.
The six-month clock starts the month a new beneficiary turns 65 and is enrolled in Part B. It runs whether or not the mail gets opened.
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