A Simple Guide to Medicare Supplement (Medigap) Plans

Medicare is the federal health insurance plan for adults in the United States age 65 and older and for younger people who have certain qualifying disabilities or health conditions.

Eligible beneficiaries typically receive benefits through Original Medicare (Part A and Part B) which is provided by the federal government, or through a privately-sold Medicare Advantage plan, which is also called Part C.

Original Medicare coverage does leave some out-of-pocket cost gaps in care that beneficiaries must account for as part of their coverage plan, such as deductibles, copays, coinsurance and more. Seniors who enroll in Original Medicare may be able to apply for a Medicare Supplement (Medigap) plan that are available on a state-by-state basis in order to get coverage for some of the out-of-pocket costs. 

Medicare supplement plans are commonly known as Medigap because of the way they plug major gaps in coverage left by many Medicare plans. Medigap plans are bound by state and federal laws, both for coverage limits and for policy billing practices.

Several Medigap supplemental insurance plans are available that offer a range of premiums, deductibles and coinsurance requirements. Original Medicare beneficiaries can shop around among plans available in their state to find a policy package that’s best for them. In most states, there are 10 standardized Medicare Supplement plans, which we outline below.

You can learn more about Medicare Supplement plans and compare plans available where you live online or by calling to chat with a licensed insurance agent.

Medicare Supplement Plan Options

Medicare Supplement plans are standardized across state lines, with a limited number of plan options offered for beneficiaries to choose from.

In most states, standardized Medigap plans are designated by the plan letters A, B, C, D, F, G, K, L, M and N (Massachusetts, Wisconsin and Minnesota standardize their plans differently).

Gaps in this letter sequence (such as Plan E or Plan J) correspond to former plan options that are no longer available for new enrollees.

Medigap plan letters are not to be confused with Original Medicare Parts A, B, C or D. Medicare parts are different basic care options, while Medigap letters are different Medicare Supplement Insurance plan options. 

Each of the 10 standardized Medicare supplement plans available in 2024 offer full Medicare Part A coinsurance coverage plus up to 365 days of inpatient care beyond the Medicare Part A maximum allotment.

All plans also offer partial or total Part B coinsurance coverage. Plans K and L pay only 50% and 75% of the Part B coinsurance, however, and Plan N leaves a relatively small number of office visits and other services open to $20 to $50 co-payments.

Medigap Plan F and Plan G offer high-deductible options, which offer lower monthly premiums in exchange for a high annual deductible.

Two popular Medigap plans, Plan C and Plan F, are no longer available to new Medicare beneficiaries who first became eligible after January 1, 2020, though current beneficiaries of Plan F and Plan C can keep their current plan. If you were eligible for Medicare before Jan. 1, 2020, you can also still enroll in Plan F or Plan C if either is available where you live.

Enrolling in Medicare Supplement Plans

Medicare beneficiaries can enroll in a Medigap plan just as they can with any insurance policy. Many enrollees simply sign up for a policy at the company’s website or through a state health exchange.

For states with one authorized Medigap provider, this can be easy enough, though some extra research may be needed for bigger states with more options.

Qualified Medicare planners can often be a valuable source of information about locally available Medicare supplement plans, as can healthcare providers or staff at a senior care facility through word of mouth. 

Medigap Enrollment Windows

After choosing a plan, beneficiaries are encouraged to apply during their Medigap Open Enrollment Period period. Enrollees who apply outside of their open enrollment period could pay a penalty fee on top of the regular plan premium, and in 47 states insurers are permitted to apply normal underwriting standards, which could result in permanently higher premiums or even a denial of coverage.

When beneficiaries apply during their Medigap Open Enrollment Period, they have what are called guaranteed issue rights. When an applicant has a guaranteed issue right, they can apply for a Medigap plan and the insurance company selling the plan can’t use underwriting to charge them a higher fee for their plan or deny them coverage altogether.

Medicare beneficiaries applying for coverage can generally do so with guaranteed issue rights during their Medigap Open Enrollment Period.

Medigap Open Enrollment Period

Medicare beneficiaries can first apply for a Medigap policy around the time they become eligible for Original Medicare. A beneficiary’s Medigap Open Enrollment Period is a six-month period that begins as soon as they are at least 65 years old and are enrolled in Medicare Part B.

If you don’t apply for a Medicare Supplement plan during your Medigap Open Enrollment Period, you may still be able to apply for a plan any other time of the year if you qualify for a guaranteed issue right. If you don’t qualify for a guaranteed issue right, however, you could face medical underwriting and could be charged more or denied coverage.

Can People Under 65 Apply For Medicare Supplement Insurance?

You may also be able to apply for a Medigap plan if you are under 65 and have a long-term disability, though many states do not require insurance companies to sell Medigap policies to people under age 65.

Under some circumstances, new enrollees must wait up to six months before Medigap coverage kicks in, though this waiting period can be waived if the gap in your “creditable coverage” is 63 days or less in duration. 

Note that Medicare Supplement plans are only available to seniors enrolled in Original Medicare, specifically Part B. Medigap policies cannot legally be sold to beneficiaries enrolled in a Medicare Advantage plan.