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Medicare open enrollment runs annually from Oct. 15 to Dec. 7 and lets beneficiaries make certain changes to Medicare coverage. Medigap open enrollment is a separate, one-time six-month period tied to turning 65 and enrolling in Part B, when insurers generally cannot deny a policy or charge more because of pre-existing health conditions.
A Seniors Guide report on the differences between Medicare and Medigap enrollment periods says beneficiaries should not confuse Medicare’s annual Oct. 15–Dec. 7 window with Medigap’s one-time six-month enrollment period. The distinction matters because the Medigap window provides specific protections against health-based coverage denials and higher premiums that may not apply after it ends.
During annual Medicare open enrollment, people can review and make eligible changes to their Medicare coverage, including switching between Original Medicare and Medicare Advantage, or comparing Part D prescription drug plans. The source identifies the 2026 period as Oct. 15 through Dec. 7. The period is recurring; it is not the same as the initial enrollment period for someone first becoming eligible for Medicare.
Medigap, also called Medicare Supplement Insurance, is sold by private insurers to help pay certain out-of-pocket costs associated with Original Medicare, such as coinsurance, copayments and deductibles. A person must have Original Medicare Part A and Part B to buy a Medigap policy; Medigap cannot be used with Medicare Advantage. Its six-month open enrollment period starts on the first day of the month when a person is both at least 65 and enrolled in Part B, according to the report’s account of Medicare rules.
During those six months, the report says, a beneficiary can buy any Medigap policy the insurer sells and cannot be denied because of a pre-existing health problem. Afterward, people may still be able to apply, but insurers in most states can use medical underwriting, which may result in a denial or higher premiums based on health. The report cautions that later access depends on applicable rules and circumstances; a policy may not be available or may cost more.
How the Two Windows Affect Coverage
The difference is consequential for people weighing coverage around age 65 or after enrolling in Part B. Medicare’s annual window allows certain changes to Medicare coverage, but it does not restart the separate Medigap six-month protection. Someone who misses that Medigap period should not assume a future Medicare open enrollment will provide the same guaranteed access to a supplement policy.
That can affect both choice and cost. A beneficiary who wants Original Medicare with help paying its cost-sharing may have fewer Medigap options later if medical underwriting applies. Conversely, a Medigap policy is not a substitute for comparing Part D drug coverage: the report says policies sold after 2005 do not include prescription drug coverage, so people seeking drug benefits generally need a separate Part D plan.
The rules also matter when comparing Original Medicare with Medicare Advantage. Medigap is designed to supplement Original Medicare, not Medicare Advantage, so beneficiaries considering a switch should check which coverage they can use and what protections apply before making a change. Individual eligibility and state rules can affect the available choices.
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Medigap’s One-Time Protection
The report distinguishes three timelines. Medicare’s initial enrollment period is a seven-month window that begins three months before a person’s 65th birthday month, includes that month and continues for three months afterward. Medicare open enrollment, by contrast, is an annual opportunity to make specified coverage changes. Medigap open enrollment is tied to age 65 or older and Part B enrollment, and its six-month clock runs only once.
Medigap policies help cover certain Original Medicare out-of-pocket expenses, but they do not cover every service. The source lists long-term care, most dental and vision care, hearing aids and private-duty nursing among items not covered. Prescription drug coverage is separate for policies sold after 2005. Policy benefits and availability can vary: most states use standardized plan types, while Massachusetts, Minnesota and Wisconsin standardize Medigap policies differently. The report also notes that Medicare SELECT policies are available in some states and have specific switching provisions.
The article cites KFF figures reported by Kiplinger: Plan G accounted for 46% of Medigap policyholders in 2025, while Plan F was estimated at roughly 30% to 36%. The source says full-year 2026 data was not yet available; those figures describe policyholder shares, not the proportion of all Medicare beneficiaries enrolled in Medigap.
“The Medigap open enrollment period is a six-month window”
— Medicare, as described in the Seniors Guide report
Eligibility Depends on Individual Circumstances
The report does not describe every state-specific rule or every circumstance that can create guaranteed rights to buy Medigap outside the standard six-month period. Whether an applicant can enroll later, and whether an insurer can apply medical underwriting, depends on applicable federal and state protections and the person’s situation. The report also does not provide insurer-specific premiums or policy availability.
The cited Plan G and Plan F figures are historical estimates for 2025, and the source says full-year 2026 data was not available. They should not be treated as current-year enrollment totals. Medicare plan choices and costs can also vary by location and individual coverage needs.
Check Dates Before Changing Coverage
People approaching 65 or enrolling in Part B should identify when their Medigap six-month period begins, then compare available policies while its protections apply. Those reviewing Medicare coverage for 2026 can use the Oct. 15–Dec. 7 annual window to examine eligible plan changes, including Medicare Advantage and Part D options. Before switching, beneficiaries should confirm how the change affects access to Original Medicare and Medigap.
The report advises researching policies and checking relevant protections, particularly because policy costs and underwriting practices may differ. For decisions about eligibility, coverage and enrollment deadlines, beneficiaries can verify their circumstances with Medicare, their state insurance department or a qualified benefits counselor.
Key Questions
Are Medigap and Medicare open enrollment the same?
No. Medicare open enrollment is an annual period for eligible Medicare coverage changes. Medigap open enrollment is a separate, one-time six-month period tied to being at least 65 and enrolled in Part B.
When does the Medigap six-month period begin?
According to the report, it begins on the first day of the month when you are both 65 or older and enrolled in Medicare Part B.
Can I buy Medigap if I have Medicare Advantage?
No. The report says Medigap is available to people with Original Medicare, Part A and Part B; it does not supplement Medicare Advantage.
Can I get a Medigap policy after the six-month window?
Possibly, but the report says that in most states insurers may use medical underwriting after the protected period. An insurer may deny an application or charge more based on health, subject to applicable protections and individual circumstances.
Does Medigap include prescription drug coverage?
Medigap policies sold after 2005 do not include prescription drug coverage, according to the report. People seeking that coverage generally need to consider a separate Part D plan.
Source: seniorsguide.com
