Buying a Medicare Supplement Insurance policy, commonly called Medigap, is less a matter of shopping around and more a matter of timing. A six-month window opens the first day of the month a person turns 65 and is enrolled in Medicare Part B, and for that stretch only, federal law strips insurance companies of the power to say no. Outside that window, buying a Medigap policy looks a lot more like buying any other individual insurance product, complete with health questions and the possibility of being turned down.
The One-Time Window Insurers Cannot Ignore
During the Medigap Open Enrollment Period, an insurance company selling Medigap policies in a state must sell any of them to an applicant, and cannot deny coverage or charge a higher premium because of past or present health problems, according to Medicare’s own guidance on when to buy. There is no medical underwriting during this period; a cancer diagnosis, a heart condition, or any other pre-existing issue cannot be used to deny the application or price it differently. The window lasts six months and does not repeat. Once it closes, Medicare is explicit that there is no federal guarantee an insurance company will sell a policy at all, and if one is available, it may cost more depending on the applicant’s health history. Because the trigger is enrollment in Part B rather than a birthday alone, someone who delays Part B while covered by an employer plan does not start the clock until that later enrollment happens, which can push the window well past age 65 for people who are still working.
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What Happens Once a Buyer Is Locked In
The trade-off for the narrow shopping window is a policy that is difficult to lose once it is bought. Standardized Medigap policies renew automatically every year, even if the policyholder develops serious health problems afterward, according to Medicare’s explanation of how Medigap works. An insurance company can only drop a Medigap policyholder for one of three reasons: the premiums stop being paid, the original application contained false information, or the insurer itself goes bankrupt or otherwise leaves the business. A diagnosis received five or ten years into a policy has no bearing on the insurer’s ability to keep covering the person, a protection that only exists because the underwriting decision was already made, and closed, back at the six-month window. Standardized Medigap plans are also required to cover one person only, so a married couple who both want Medigap coverage each has to shop and qualify separately, which makes the timing of each spouse’s own six-month window, not just one household window, the relevant deadline.
Why Missing the Window Tends to Be the Costlier Mistake
Some people delay buying a Medigap policy because they are still working, still covered by an employer or union plan, or simply because they have not needed extra coverage yet. That can be a reasonable choice, but it carries a real cost if health changes before a policy is ever purchased. Outside a few specific guaranteed-issue situations, an insurer that would have had to accept an applicant automatically during the six-month window is free to evaluate that same applicant’s health history once the window has passed, and free to charge accordingly or decline the application. The six-month period is the one point in a person’s Medicare timeline when a health condition, however serious, cannot be used against a Medigap application. Missing it does not always close the door, but it hands the underwriting leverage to the insurer instead of the applicant. Some states go further than federal law requires and offer additional protections, such as an annual window to switch Medigap policies without new underwriting, but those are state-specific add-ons rather than a nationwide guarantee, and a Medigap shopper cannot assume one applies without checking the rules where they live.
What to Confirm Before the Window Opens
Because the window is triggered by Part B enrollment rather than by a calendar reminder from any insurer, the timing is easy to miss for someone who delays signing up for Part B while still working. Confirming the exact month Part B coverage starts is the first step, since that date, not a birthday alone, is what starts the six-month clock. Comparing available Medigap plans in the state before that window opens, rather than during it, gives an applicant time to choose deliberately instead of rushing a decision inside a period that only lasts six months and does not come back. Because Medigap plans are standardized by letter, with the specific benefits attached to each letter set by law rather than by the individual insurance company, most of the comparison work at that stage comes down to premium and insurer reputation rather than reading fine print about what a given plan actually covers.
This article was produced with the assistance of AI and reviewed by The Financial Wire editorial team.
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David M. Keller is a finance writer based in Columbus, Ohio, covering personal finance and consumer-focused economic topics. He earned his degree in journalism from Ohio University and began his career reporting on local business and economic trends for a regional media outlet. Since then, he has contributed to a variety of online publications, focusing on clear, practical coverage of topics such as cost of living, debt, and everyday financial decision-making.
