Medicare Supplemental Insurance (Medigap) can be a little confusing for people who have just started to research their retirement health-insurance options.
No surprise there.
During your working years, you typically have a single insurance plan that provides the entirety of your medical coverage each year. Past that, the only other “assistance” you might get is the use of a health savings account (HSA) or flexible spending account (FSA), which allows you to allocate pretax dollars to certain qualified expenditures. And that’s about it.
However, once you leave work-provided coverage behind and switch to Medicare, a number of things change—and that includes eligibility for Medigap.
Today, I’m going to explain how Medigap works, the costs, and the enrollment process. Once you know these basics, you should have a better idea about whether or not Medigap makes sense for you.
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How Does Medigap Work?
As the name implies, Medicare Supplement Insurance is a plan purchased in addition to Medicare that can help pay for out-of-pocket costs that aren’t covered by Medicare: predominantly coinsurance, copayments, and deductibles.
Original Medicare beneficiaries have the option to buy Medigap; people with Medicare Advantage (Part C) do not. But similar to Medicare Advantage, these plans are purchased through private insurers.
Related: What Is Medicare? A Guide to Types of Medicare Coverage
Medigap works with any hospital or doctor who accepts Medicare, which is the vast majority of providers. For instance, according to health policy nonprofit KFF, only about 1% of all non-pediatric physicians formally opted out of the Medicare program in 2024.
How Many Medigap Plans Are There?
The policy you choose determines how much coverage you receive. Like with Medicare, Medigap plans are identified by letter (“Plan A,” “Plan B,” etc.). Medicare.gov lists 10 plans: A-D, F-G, and K-N.
Plans that carry the same letter must offer the same basic benefit, so price is generally the biggest difference. You can compare Medigap plans on Medicare.gov.
Note: Massachusetts, Minnesota, and Wisconsin Medigap policies are standardized differently.
What Is Medicare SELECT?
Some states let you buy Medicare SELECT, yet another type of Medigap policy that requires to use specific in-network doctors and hospitals.
Medicare SELECT enrollees can switch to a standard Medigap policy within 12 months if they decide they want that instead of a SELECT policy.
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How Much Does Medigap Cost?
Pricing for Medicare Supplemental Insurance can vary substantially by state, plan, and age. For example, the average Plan N premiums for 65-year-olds in 2026 is $122.98, per data from MedicareSupplement.com. Comparatively, the average Plan F premium for an 85-year-old this year is $321.64.
Depending on which Medigap plan you choose, you might or might not have a deductible. For 2026, the annual deductible amount for Medigap plans F, G, and J is $2,950.
Two plans—Plans K and L— have maximum out-of-pocket limits. In 2026, those maximums are $8,000 for Plan K, and $4,000 for Plan L. After a person reaches their maximum, the plan pays for 100% of their costs for approved services for the rest of the year.
Related: Medicare FAQs: Your Questions Answered
When Do I Enroll in Medigap?
Your Medigap Open Enrollment Period begins the first month you have Medicare Part B and you’re 65 or older. This is a one-time enrollment period that lasts for six months; it does not repeat every year.
You can enroll in any Medigap policy during this time. Insurance companies can’t refuse to sell you any of their policy offerings. Additionally, they can’t use medical underwriting to determine whether to accept your application or deny you coverage because of pre-existing health issues. They can’t charge you more for pre-existing medical problems or make you wait for coverage to start either.
Following your Open Enrollment Period:
- Fewer policy options may be available to you.
- You might have to pay more.
- Insurance companies are allowed to deny you policies if you don’t meet their medical underwriting requirements.
However, if your other health coverage changes, you might have a “guaranteed issue right” situation in which insurance companies can’t deny you a Medigap policy, must cover all your pre-existing conditions, and can’t charge you more based on your health history or current health situation.
If you’re unsure when you can buy a Medigap policy, you can answer a few questions on the Medicare website to find out.
Related: Original Medicare vs. Medicare Advantage: How Do These Plans Differ?
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