Medicare Supplement Insurance: A Complete Guide for 2026

Medicare Supplement Insurance, commonly known as Medigap, is private health coverage that pays for out-of-pocket costs Original Medicare leaves behind, including deductibles, copayments, and coinsurance. For the more than 65 million Americans enrolled in Medicare according to the Centers for Medicare & Medicaid Services (CMS), these supplemental policies can mean the difference between predictable healthcare spending and exposure to substantial unexpected bills. This guide explains how Medicare Supplement Insurance functions, what each standardized plan covers, what it costs, and how to evaluate your options as of 2026.

What Medicare Supplement Insurance Actually Is

Medicare Supplement Insurance is a category of private insurance designed to work alongside Original Medicare (Part A hospital coverage and Part B medical coverage). It does not replace Medicare. Instead, after Medicare pays its share of an approved healthcare service, your Medigap policy pays some or all of the remaining costs depending on the plan you select.

According to the Kaiser Family Foundation, roughly 4 in 10 beneficiaries in Original Medicare rely on a Medigap policy to supplement their coverage. The plans are standardized by federal law in most states, meaning a Plan G sold by one carrier offers the identical benefits as a Plan G sold by another, even though premiums vary substantially.

Three states — Massachusetts, Minnesota, and Wisconsin — standardize Medigap differently under their own state rules. Medigap policies also do not cover prescription drugs; that benefit is purchased separately through a Medicare Part D plan. Understanding this division of coverage is essential before comparing policies.

How Medigap Works With Original Medicare

When you receive a Medicare-covered service, the provider bills Medicare first. Medicare pays its approved share — typically 80% of the Part B allowable amount after the annual deductible. The claim is then automatically forwarded to your Medigap insurer, which pays its portion based on the plan you hold. You generally receive no balance bill for Medicare-approved services if you carry a comprehensive plan like Plan G.

This coordination is seamless because federal regulations require Medigap carriers to participate in electronic crossover billing. You can use any provider in the United States that accepts Medicare, with no network restrictions. That portability is a key reason retirees who travel or split residency between states often prefer Medigap to Medicare Advantage.

Medigap does not cover services Medicare itself excludes, such as routine dental, vision, hearing aids, or long-term custodial care. It also does not pay for services received outside the U.S. unless your plan includes the optional foreign travel emergency benefit, which is standard in Plans C, D, F, G, M, and N.

The Standardized Plans Available Today

Federal law identifies Medigap plans by letter: A, B, C, D, F, G, K, L, M, and N. Each letter corresponds to a fixed set of benefits. Plans C and F are no longer available to people who became eligible for Medicare on or after January 1, 2020, because of the Medicare Access and CHIP Reauthorization Act (MACRA), which prohibits new plans from covering the Part B deductible.

For most newly eligible beneficiaries, Plan G is the most comprehensive option available. It covers:

• Part A hospital coinsurance and an additional 365 days after Medicare benefits are used
• Part B coinsurance or copayments
• The first three pints of blood
• Part A hospice coinsurance
• Skilled nursing facility coinsurance
• Part A deductible
• Part B excess charges
• Foreign travel emergency care (up to plan limits)

Plan N is a popular lower-premium alternative that requires small copays for office and emergency room visits and does not cover Part B excess charges. Plans K and L offer cost-sharing structures with annual out-of-pocket limits.

What Medicare Supplement Insurance Costs

Premiums vary widely by ZIP code, age, gender, tobacco use, and the carrier’s pricing method. According to the latest market data from the National Association of Insurance Commissioners (NAIC), monthly premiums for Plan G typically range from about $100 to over $300 depending on geography and underwriting class. Plan N generally runs 20% to 30% less.

Three pricing structures are used:

• Community-rated: Everyone pays the same premium regardless of age.
• Issue-age-rated: Premiums are based on your age when you bought the policy and do not increase due to aging.
• Attained-age-rated: Premiums rise as you get older. This is the most common method and typically appears cheapest at age 65.

All policies are also subject to annual rate increases tied to medical inflation. When comparing carriers, ask for the company’s rate-increase history over the past five to ten years. A low introductory premium from an attained-age carrier may become more expensive than a stable community-rated policy by your mid-70s.

Enrollment Windows and Guaranteed Issue Rights

The most important rule in Medigap is timing. Your Medigap Open Enrollment Period is a one-time, six-month window that begins the month you turn 65 and are enrolled in Medicare Part B. During this period, federal law guarantees you the right to buy any Medigap plan sold in your state at the best available rate, regardless of pre-existing conditions.

Outside this window, in most states, insurers can use medical underwriting to deny coverage or charge higher premiums based on your health. A handful of states — including New York, Connecticut, Massachusetts, Maine, and Washington — offer broader continuous or annual guaranteed issue rights, but most do not.

You may also qualify for guaranteed issue rights in specific circumstances, such as when an employer group plan ends, when a Medicare Advantage plan leaves your service area, or during the Medicare Advantage trial period within the first 12 months of joining a Medicare Advantage plan. Missing your initial window can permanently limit your options, so this decision deserves careful timing.

Medigap vs. Medicare Advantage

Medicare Supplement Insurance and Medicare Advantage (Part C) are mutually exclusive — you cannot legally hold both. Medicare Advantage replaces Original Medicare with a private bundled plan, often including drug coverage and extra benefits like dental or vision, typically with low or zero monthly premiums but with provider networks and prior authorization requirements.

Medigap, by contrast, layers on top of Original Medicare. It costs more in monthly premium but offers predictable out-of-pocket expenses, nationwide provider access, and no referrals. According to KFF research, Medicare Advantage enrollees are more likely to report cost-related access problems than those with Medigap coverage.

The right choice depends on your health status, budget, travel patterns, and tolerance for managed-care rules. People with chronic conditions and frequent specialist visits often benefit from the predictability of Medigap. Those in stable health who value lower premiums and bundled extras may prefer Medicare Advantage. Switching from Advantage back to Medigap later can be difficult because of underwriting, so the initial choice carries long-term weight.

What Experts Recommend

Independent insurance counselors associated with State Health Insurance Assistance Programs (SHIPs) — the federally funded counseling network available in every state — consistently advise beneficiaries to enroll in Medigap during their initial six-month open enrollment period if they intend to use it, because guaranteed issue rights are difficult to recover later.

Most independent brokers and consumer advocates recommend Plan G or Plan N for newly eligible enrollees, citing the combination of comprehensive benefits and reasonable pricing. Plan F, while still available to those eligible before 2020, is generally discouraged for current shoppers because closed plans tend to experience faster rate increases as their risk pool ages.

Experts also emphasize three practical rules: shop multiple carriers because benefits are identical but premiums are not; review the insurer’s complaint ratio through your state department of insurance; and revisit your policy every few years to ensure your premium remains competitive. Working with a licensed independent broker who represents multiple carriers, rather than a captive agent, generally produces broader comparisons.

When to Consult a Licensed Professional

Medicare decisions are financially significant and can be difficult to reverse. If you are approaching 65, losing employer coverage, returning to the U.S. from abroad, or considering a switch between Medicare Advantage and Original Medicare with Medigap, a licensed Medicare broker or your local SHIP counselor can model your specific scenario. SHIP counseling is free and unbiased; broker services are also free to consumers because brokers are paid by carriers.

You should also consult a professional before making changes if you have chronic conditions, are currently in active treatment, or live in a state with restrictive underwriting rules. As of 2026, federal Medigap rules remain governed by MACRA and CMS regulations, but state-level reforms continue to evolve, particularly around guaranteed issue rights and birthday rules in states like California, Oregon, Idaho, and Illinois. Verify current rules with your state department of insurance before finalizing any policy decision.

Frequently Asked Questions

What does Medicare Supplement Insurance actually cover?

Medicare Supplement Insurance, or Medigap, covers out-of-pocket costs left behind by Original Medicare, including the Part A hospital deductible, Part A and B coinsurance, hospice coinsurance, skilled nursing facility coinsurance, and the first three pints of blood. More comprehensive plans like Plan G also cover Part B excess charges and foreign travel emergency care. Medigap does not cover prescription drugs, routine dental, vision, hearing aids, or long-term custodial care. For drug coverage, you need a separate Medicare Part D plan. Specific benefits depend on which standardized plan letter you choose, and benefits are identical across carriers for the same plan letter.

How much does a Medigap plan cost per month?

Monthly premiums for Medicare Supplement Insurance vary widely based on your ZIP code, age, gender, tobacco use, and the carrier’s pricing method. According to the latest National Association of Insurance Commissioners data, Plan G premiums typically fall between roughly $100 and $300 per month, with Plan N usually 20% to 30% lower. Premiums also rise annually with medical inflation and, under attained-age pricing, with your age. Because benefits are standardized by federal law, two policies with the same plan letter offer identical coverage, so shopping multiple carriers can produce significant savings on identical benefits.

When is the best time to enroll in Medicare Supplement Insurance?

The best time to enroll is during your Medigap Open Enrollment Period, the six-month window that starts the month you turn 65 and are enrolled in Medicare Part B. During this period, federal law requires insurers to sell you any plan offered in your state at the best available rate, regardless of your health history. Outside this window, most states allow medical underwriting, meaning insurers can deny coverage or charge higher premiums based on pre-existing conditions. Missing this window can permanently limit your options, so timing this decision carefully is one of the most important steps in Medicare planning.

Can I switch from Medicare Advantage to a Medigap plan later?

You can request to switch, but acceptance is not guaranteed in most states after your initial enrollment period. If you are outside a guaranteed issue situation, insurers can use medical underwriting and deny your application based on health. There are limited protected windows, including the Medicare Advantage trial right in your first 12 months on an Advantage plan and certain involuntary plan terminations. A few states, such as Connecticut, New York, Maine, and Massachusetts, offer broader continuous or annual rights to enroll in Medigap. Check with your state department of insurance or a SHIP counselor before assuming you can switch.

Is Plan G or Plan N better for new enrollees?

Both are popular choices for people newly eligible for Medicare. Plan G is the most comprehensive plan available to those who became eligible on or after January 1, 2020, covering everything except the Part B deductible. Plan N has lower premiums but requires small copays — up to $20 for office visits and up to $50 for emergency room visits that do not result in admission — and does not cover Part B excess charges. Plan G is generally better for those who want maximum predictability, while Plan N suits people comfortable with modest copays in exchange for a lower monthly premium.

Does Medicare Supplement Insurance cover prescription drugs?

No. Medicare Supplement Insurance does not include prescription drug coverage for policies sold today. To get outpatient drug coverage, you must enroll separately in a Medicare Part D prescription drug plan offered by a private insurer approved by Medicare. Failing to enroll in Part D when you are first eligible can trigger a permanent late enrollment penalty added to your premium for as long as you have Part D coverage. Some older Medigap policies sold before 2006 included drug benefits, but those plans are no longer available to new enrollees, and current Medigap shoppers should plan for a separate Part D policy.

Are Medigap plans the same in every state?

Medigap plans are standardized by federal law in 47 states, meaning a Plan G from one carrier provides the same core benefits as a Plan G from another. Three states — Massachusetts, Minnesota, and Wisconsin — standardize their plans under separate state rules. Premiums, however, are never standardized and vary significantly by carrier, ZIP code, and pricing method. Some states also add consumer protections such as annual birthday rules, which allow current policyholders to switch plans without underwriting during a defined window. California, Oregon, Idaho, and Illinois are notable examples, though specific rules differ, so verify protections with your state department of insurance.

Do I need Medigap if I'm relatively healthy?

That depends on your tolerance for financial risk. Original Medicare has no annual out-of-pocket maximum, which means a serious illness or hospitalization could expose you to significant costs even if you rarely use medical care today. Medigap converts that unpredictable risk into a fixed monthly premium. Healthy beneficiaries who skip Medigap initially often find it difficult or expensive to enroll later because of medical underwriting outside the initial six-month open enrollment window. If you value predictable costs, nationwide provider access, and avoiding referrals or prior authorizations, Medigap remains valuable even when you are healthy.