*8 min read ยท Last updated May 26, 2026*
In this article
– The six-month window most people do not use – What medical underwriting actually means for a Medigap application – The guaranteed-issue rights that survive after open enrollment closes – States that protect you beyond the federal floor – FAQ
Rosa Beltran, 71, lives in San Antonio and has been on a Medicare Advantage plan since the month she turned 65. Her primary care physician stayed in the plan’s network for six years. In March, her doctor’s group left the network. Rosa called three Medigap carriers to ask about switching to Original Medicare paired with a Plan G supplement so she could keep the doctor. The first carrier reviewed her medical questionnaire, noted Type 2 diabetes managed with metformin and stage 2 chronic kidney disease, and declined. The second declined as well. The third offered a Plan G policy with a 50 percent rate-up on the standard premium, raising her monthly cost from $148 to $222. Inside her original Medigap open enrollment window, every one of those carriers would have been required to issue the same Plan G at the same standard rate.
The six-month window most people do not use
When a Medicare beneficiary first enrolls in Part B at age 65 or later, federal law creates a one-time, six-month Medigap Open Enrollment Period. Inside that window, every Medigap carrier licensed in the beneficiary’s state is required to issue any Medigap plan the beneficiary applies for, at the carrier’s standard rate, without medical underwriting. Pre-existing conditions are not a factor. Carriers can apply a six-month pre-existing condition waiting period for conditions diagnosed in the six months before the policy effective date, but the policy issues.
The window has no second chance under federal law. It does not reset if the beneficiary takes a Medicare Advantage plan first, decides later to switch to Original Medicare, moves to a different state, or loses other coverage. Beneficiaries who chose Medicare Advantage at 65 because their doctor or hospital was in network, and who later want to move to Original Medicare paired with a Medigap supplement, often find the open enrollment window expired five or ten years ago.
DIN has covered the basics of what Medicare covers for beginners and the structural difference between Medicare Advantage and Medicare Supplement plans. The six-month window is the bridge between those two articles and the most consequential calendar date in Medicare beyond the Initial Enrollment Period itself.
What medical underwriting actually means for a Medigap application
Outside the open enrollment window and outside a guaranteed-issue scenario, a Medigap application is medically underwritten. The carrier reviews a health questionnaire that typically asks about diabetes, heart disease, kidney disease, cancer history, recent hospitalizations, prescription medications, and lifestyle factors. The carrier compares the answers against its own underwriting guidelines and the actuarial assumptions priced into its rate filings.
Three outcomes are possible. Issue at the standard rate if the answers fall within standard underwriting tolerance. Issue at a substandard rate, also called a rate-up, where the premium is multiplied by a factor that often runs 25 to 75 percent above standard. Decline if the conditions exceed the carrier’s appetite, with no policy offered.
The underwriting guidelines vary by carrier. A Type 2 diabetes case with an A1C below 7.0, no complications, and stable medication can be a standard issue at one carrier and a 25 percent rate-up at another. Active cancer treatment within the last two years is a near-universal decline. End-stage renal disease, congestive heart failure with reduced ejection fraction, and recent stroke commonly trigger declines across the market.
The application is single-carrier, which means the applicant can shop. A decline at one Medigap carrier does not bar an application at another. The applicant typically has to disclose prior declines on subsequent applications, which complicates but does not necessarily kill the next conversation.
The guaranteed-issue rights that survive after open enrollment closes
Federal law preserves a narrow set of guaranteed-issue rights outside the open enrollment window. The most common scenarios:
Involuntary loss of employer or union health coverage that was paying secondary to Medicare. The beneficiary has 63 days to apply for a Medigap plan with guaranteed issue.
Medicare Advantage trial right within the first 12 months of being newly enrolled in Medicare Advantage at age 65, or within the first 12 months of switching from a Medigap policy to Medicare Advantage for the first time. The Medicare Advantage 12-month trial right window covers this scenario in detail.
Medicare Advantage plan termination, withdrawal from the service area, or carrier insolvency. The beneficiary gets guaranteed-issue rights to specific Medigap plans (typically Plan A, B, C, D, F, G, K, or L depending on situation and birth year) within 63 days.
SELECT plan move where the beneficiary moves out of the service area of a Medicare SELECT policy and qualifies for guaranteed-issue switch to standard Medigap.
Misrepresentation by a Medicare Advantage plan or agent that misled the beneficiary about coverage, where the state insurance department or CMS issues a determination supporting the guaranteed-issue right.
The guaranteed-issue rights are narrower than most people assume. Voluntarily leaving Medicare Advantage in year 2 or later, outside the 12-month trial right, is not a guaranteed-issue scenario under federal law. The applicant is medically underwritten.
States that protect you beyond the federal floor
A handful of states have used their authority to expand Medigap protections beyond the federal floor.
Connecticut and New York require continuous guaranteed issue. Carriers must accept any Medigap application at any time, with no medical underwriting and no rate-ups for health reasons.
Massachusetts requires guaranteed issue annually during a defined open enrollment window each February, with no medical underwriting.
Maine requires guaranteed issue once each year on a rolling basis for Plan A.
Vermont requires continuous guaranteed issue without medical underwriting for community-rated plans.
California, Oregon, and Washington each have “birthday rule” guaranteed-issue windows. Each year around the beneficiary’s birthday (the exact length varies by state, typically 30 to 63 days), the beneficiary can switch from one Medigap plan to another Medigap plan of equal or lesser value without medical underwriting.
Where the beneficiary lives at the time of application determines which set of rules applies. Moving from a federal-floor state to a guaranteed-issue state does not automatically unlock the protections; the beneficiary needs to be a resident of the protected state on the application date.
Get Medicare Supplement, Medicare Advantage, and Part D options reviewed side by side with a licensed agent who can map the open enrollment window and the guaranteed-issue rights to your situation.
Compare Medicare plan optionsThe six-month Medigap Open Enrollment Period is the single calendar window where a Medicare beneficiary has the strongest leverage with carriers, and most people spend it without using it. Outside the window, the carrier underwrites. Inside it, the carrier issues. The decision to enroll in Medicare Advantage at 65 sets the path that the six-month window either preserves or closes.
Frequently asked questions
When does the Medigap Open Enrollment Period start? The first day of the month Part B coverage begins at age 65 or later, and it runs for six months. The window is a one-time event under federal law and does not reset.
Can a Medigap carrier deny me coverage? Yes, outside the open enrollment window and outside guaranteed-issue scenarios. Carriers can review a medical questionnaire and decline, rate up, or issue at the standard rate depending on the answers and the carrier’s underwriting guidelines.
What are Medigap guaranteed-issue rights? Specific scenarios under federal law where the carrier must accept the application without medical underwriting, including involuntary loss of employer coverage, Medicare Advantage trial-right disenrollment in the first 12 months, and Medicare Advantage plan termination or service-area withdrawal.
Which states have additional Medigap protections beyond federal law? Connecticut and New York require continuous guaranteed issue. Massachusetts has an annual February window. Maine, Vermont, California, Oregon, and Washington have their own enhanced rules ranging from birthday-rule switching to community rating.
How much can a Medigap carrier raise my premium for health reasons? Premium rate-ups outside open enrollment commonly run 25 to 75 percent above the carrier’s standard rate, depending on the conditions disclosed and the carrier’s underwriting guidelines. Standard premiums themselves vary by carrier, plan letter, age, and state.
