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Medicare’s annual Open Enrollment period, Oct. 15 through Dec. 7, lets people review or change certain Medicare coverage. Medigap Open Enrollment is a separate six-month period tied to being at least 65 and enrolled in Medicare Part B; it provides protections for buying supplemental coverage that generally do not renew each year.
A Seniors Guide report outlines a key distinction for people reviewing Medicare coverage: the annual Medicare Open Enrollment period, which runs Oct. 15 through Dec. 7, 2026, is not the same as the one-time six-month window for buying Medigap without health-based denial protections. The difference matters because the Medigap window is tied to a person’s age and Part B enrollment, and generally does not recur each year.
During Medicare Open Enrollment, beneficiaries can make certain changes to their coverage, including switching between Original Medicare and Medicare Advantage and reviewing or changing Part D prescription drug coverage. It is an annual opportunity to compare available options. The report also describes it as a period when people can enroll in Medicare, though eligibility and enrollment rules depend on individual circumstances; the usual first chance to sign up for Medicare is the separate seven-month Initial Enrollment Period around a person’s 65th birthday.
Medigap, also called Medicare Supplement Insurance, is sold by private insurers and can help pay some out-of-pocket costs under Original Medicare, including certain coinsurance, copayments and deductibles. A person must have Original Medicare Parts A and B to buy it; Medigap cannot be used with Medicare Advantage. The six-month Medigap Open Enrollment Period begins on the first day of the month in which someone is both at least 65 and enrolled in Part B.
During that six-month period, the report says, applicants can buy any Medigap policy an insurer sells and cannot be denied coverage because of a pre-existing health condition. Afterward, federal protections may no longer apply in the same way. In most states, insurers can use medical underwriting for later applications, which may mean higher premiums or a denial, although rules and guaranteed-issue rights can vary by state and circumstance.
Two Windows, Different Protections
The distinction can affect both access to supplemental coverage and its cost. Medicare Open Enrollment comes around each year and focuses on changing certain forms of Medicare coverage. It does not restart the six-month Medigap protection period. Someone who waits until a later annual enrollment period to seek Medigap may find that an insurer can review health history, depending on state law and whether a specific guaranteed-issue right applies.
That makes the timing of Part B enrollment a practical issue for people approaching 65, including those still working or covered by an employer plan. Their Medicare and employer coverage circumstances can affect when they enroll, and the Medigap clock is linked to Part B and age. The report notes that people may sign up for Medicare while still covered by an employer plan, but individuals should check how their particular coverage coordinates before making a decision.
Medigap can reduce some costs associated with Original Medicare, but it is not a substitute for every type of coverage. It generally does not cover long-term care, routine dental or vision care, hearing aids or private-duty nursing, and policies sold after 2005 do not include prescription drug coverage. People who want drug coverage generally need a separate Part D plan.
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How Medigap Fits Original Medicare
Original Medicare consists of Part A hospital insurance and Part B medical insurance. Medigap policies are designed to supplement that coverage by paying some costs that beneficiaries might otherwise owe. They are standardized in most states, but Massachusetts, Minnesota and Wisconsin use different standardization systems. Some states also offer Medicare SELECT policies, which use provider networks; the report says SELECT policyholders may have a right to switch to a standard Medigap policy within 12 months.
The report cites KFF data showing that Plan G accounted for 46% of Medigap policyholders in 2025. It says Plan F represented roughly 30%-36%, while noting that full-year 2026 data were not yet available. Plan availability and eligibility differ: for example, people newly eligible for Medicare generally cannot buy Plan F. Medigap premiums also vary, and policies do not all cover the same costs.
The two enrollment periods therefore serve different purposes. Medicare’s annual period is for reviewing eligible Medicare choices, while Medigap’s six-month period provides a time-limited opportunity to buy supplemental coverage with specific health-status protections. Neither period should be mistaken for the other.
“The Medigap open enrollment period only happens once and doesn’t repeat yearly like Medicare open enrollment.”
— Seniors Guide report
State Rules and Personal Eligibility
The report does not detail every state-specific exception to Medigap underwriting or every circumstance that can create a guaranteed-issue right outside the initial six-month window. Those rights can depend on state law and a person’s coverage history. It is also not clear from the report how a particular employer plan would coordinate with Medicare for an individual who is still working.
Premiums, policy availability and coverage details vary by insurer and location. The cited Plan G and Plan F figures describe 2025 policyholder shares, not current enrollment in 2026. Readers should verify dates, eligibility and policy terms with Medicare, their State Health Insurance Assistance Program or a qualified benefits adviser before changing coverage.
Check Dates Before Changing Coverage
People considering a Medicare change can review their current coverage and compare available options before the Oct. 15-Dec. 7, 2026 annual enrollment period. Anyone approaching 65 or enrolling in Part B should separately identify the start and end dates of their six-month Medigap window, since the annual Medicare period does not extend it.
Before buying a policy, compare premiums and benefits, confirm whether it works with Original Medicare, and check whether prescription drug coverage must be obtained separately. Those whose Medigap window has passed can ask their state insurance department or SHIP counselor about underwriting rules and any applicable guaranteed-issue protections.
Key Questions
Is Medicare Open Enrollment the same as Medigap Open Enrollment?
No. Medicare Open Enrollment is an annual period for making certain Medicare coverage changes. Medigap Open Enrollment is a separate six-month window tied to being at least 65 and enrolled in Part B, with protections for buying a Medigap policy.
When does the six-month Medigap period begin?
It begins on the first day of the month in which you are both 65 or older and enrolled in Medicare Part B. The exact dates depend on when those conditions are met.
Can I buy Medigap if I have Medicare Advantage?
Medigap is designed to supplement Original Medicare, so you generally need Parts A and B and cannot use a Medigap policy with Medicare Advantage. People considering a change should verify the rules and timing before switching.
Can an insurer deny me Medigap after the six-month period?
In most states, an insurer may use medical underwriting after the initial Medigap period, which can affect eligibility or premiums. State rules and guaranteed-issue circumstances vary, so check the protections that apply to your situation.
Does Medigap include prescription drug coverage?
Medigap policies sold after 2005 do not include prescription drug coverage, according to the report. People seeking drug benefits generally need to consider a separate Medicare Part D plan.
Source: seniorsguide.com
