InsuranceSep 29, 2026
Medicare Supplement (Medigap) Plans Explained: What Each Letter Covers
Key takeaways Medigap plans are standardized by letter, so Plan G from one insurer covers exactly the same benefits as Plan G from any other insurer in the same state. Only the premium changes. Plan C and Plan F are closed to anyone newly eligible for Medicare on or after January 1, 2020, leaving Plan G as the most comprehensive option most new enrollees can buy. Your one-time, six-month Medigap Open Enrollment Period, which starts the month you turn 65 and enroll in Part B, is the only time most people are guaranteed a policy regardless of health history. Massachusetts, Minnesota, and Wisconsin use their own non-standardized Medigap systems, and several other states offer added protections like birthday rules or annual guaranteed-issue windows. Medigap and Medicare Advantage can't be combined. Choosing between them is a decision about which Medicare structure fits you, not a question of layering one on top of the other. Original Medicare was never designed to cover everything. Once you turn 65 and enroll, you quickly learn that Part A and Part B leave real costs uncovered. A hospital deductible here, a 20% coinsurance bill there, no cap on what you could owe in a bad year. Medicare Supplement Insurance, better known as Medigap, exists to pick up exactly those uncovered costs, and it does that job through ten standardized plans, each identified by a single letter. The letters are where a lot of people get stuck. Plan G, Plan N, Plan K, an old Plan F a neighbor swears by. It looks like alphabet soup until you understand one thing: Every plan with the same letter covers the exact same benefits, no matter which insurance company sells it. Once that clicks, the decision stops being about picking a mysterious code and becomes a straightforward question of how much coverage you want and how much you're willing to pay for it. This guide walks through what each letter covers, what these plans cost in 2026, and the timing rules that can make or break your ability to get one at a fair price . Why does Original Medicare need a supplement at all? Medicare Part A and Part B cover a lot, but they were designed around cost-sharing, not full coverage. In 2026, the Part A deductible for a hospital stay is $1,736 per benefit period (1) , and that's before any of the daily coinsurance charges that kick in for a longer stay. Part B, which covers outpatient care and physician visits, has its own annual deductible of $283 (1) , and after that, Original Medicare generally pays about 80% of approved costs, leaving you responsible for the remaining 20% with no annual cap. That last detail is the one that catches people off guard. A serious illness or a long hospital stay can generate tens of thousands of dollars in Part B coinsurance alone, and Original Medicare has no built-in stopping point. Medigap policies were created specifically to pick up some or all of that cost-sharing, which is why they're sold alongside Original Medicare rather than as a replacement for it. You keep Part A and Part B, and Medigap pays part or all of what's left over after Medicare pays its share. What do the plan letters mean? Medigap plans are standardized under federal law, which means Plan G sold by one company must cover the exact same benefits as Plan G sold by any other company in the same state. Insurers can't add or remove benefits from a lettered plan. What they can vary is the premium, the customer service, and any small extras like a gym membership discount. This is why shopping by letter first and by company second is the more useful way to think about the decision. There are ten standardized letters in most states: A, B, C, D, F, G, K, L, M, and N. Two of them, Plan C and Plan F, are closed to anyone who became newly eligible for Medicare on or after January 1, 2020. If you already had Medicare before that date, you can still buy or keep one of those two plans where they're sold. Everyone newly eligible chooses from the other eight. Here's what each one covers: Plan A covers the basics only. Part A hospital coinsurance and up to an additional 365 days of hospital costs after Medicare's own benefits run out, Part B coinsurance, the first three pints of blood, and Part A hospice coinsurance. It skips the Part A deductible, skilled nursing coinsurance, and everything related to travel or excess charges. Plan B covers everything Plan A does, plus the Part A deductible. Plan C (closed to new enrollees since 2020) adds skilled nursing facility coinsurance, the Part B deductible, and foreign travel emergency coverage on top of Plan B's benefits, making it one of the more complete plans ever sold. Plan D covers the same ground as Plan B, plus skilled nursing coinsurance and foreign travel emergency coverage, but it skips the Part B deductible. Plan F (also closed to new enrollees since 2020) covers everything, including the Part B deductible and Part B excess charges, the extra amount some doctors are legally allowed to bill above what Medicare approves. A high-deductible version of Plan F is still sold to those who qualify, requiring you to pay $2,950 in Medicare-covered costs in 2026 before the plan pays anything (2) . Plan G is the closest thing to Plan F available to anyone newly eligible for Medicare today. It covers everything Plan F does except the Part B deductible, which you pay out of pocket before the plan's other benefits apply. A high-deductible version of Plan G is also available, with the same $2,950 threshold in 2026 (2) . Plan K covers 50% of most cost-sharing, including Part B coinsurance, blood, hospice coinsurance, skilled nursing coinsurance, and the Part A deductible, while covering Part A hospital coinsurance in full. It caps your total out-of-pocket exposure at $8,000 in 2026, after which it pays 100% of covered services for the rest of the year (2) . Plan L works the same way as Plan K but covers 75% of most cost-sharing instead of 50%, with a lower out-of-pocket cap of $4,000 in 2026 (2) . Plan M covers the same benefits as Plan D, including foreign travel emergency care, but only pays half of the Part A deductible instead of the full amount. Plan N covers nearly everything Plan D does, but you pay a copay of up to $20 for some office visits and up to $50 for emergency room visits that don't result in an inpatient admission. It doesn't cover Part B excess charges. In exchange for those smaller, predictable copays, Plan N tends to carry a noticeably lower premium than Plan G. What do these plans cost? Medigap premiums vary more than the standardized benefits might suggest, and the variation comes from three separate sources. Which plan letter you pick, which insurance company you buy it from, and where you live all move the price independently of each other. The average monthly premium across all current Medigap policyholders was $217 in 2023, the most recent year with full data, according to an analysis of insurance industry data reported to state regulators (3) . That figure spans every plan type and every age group already enrolled, not just new buyers. Plan G, the most popular plan among new enrollees, averaged $164 a month among existing policyholders in that same analysis (3) . Where you live changes those numbers substantially. The same analysis of insurance industry data found the average Medigap premium ranging from $191 a month in Alaska to $267 a month in New York, and for Plan G specifically, from $140 in Washington, D.C. to $236 in New York (3) . Some of that difference comes down to how insurers are allowed to price policies. Nine states, including New York, Connecticut, and Minnesota, require community rating, where every enrollee pays the same premium regardless of age, while most other states allow attained-age rating, where your premium rises each year as you get older (3) . A policy that looks cheap at 65 under attained-age pricing can cost considerably more by 75, so it's worth asking an insurer which pricing method it uses before comparing quotes on premium alone. The insurance company you choose counts just as much as the state you live in. Because Medigap benefits are standardized by letter, price is the only real variable left between insurers selling the identical plan, which is why comparing quotes from several companies before enrolling is one of the only ways to control what you pay. When should you buy one? Timing counts for more with Medigap than with almost any other Medicare decision, because of a rule most people don't learn about until it's too late. Under federal law, you get a one-time, six-month Medigap Open Enrollment Period that starts the first month you're both 65 or older and enrolled in Medicare Part B (4) . During this window, an insurance company can't refuse to sell you any Medigap policy it offers, can't charge you more because of your health history, and can't make you wait for coverage of a pre-existing condition, except in limited circumstances. This is what's known as guaranteed issue. Once that six-month window closes, the protections mostly disappear. In nearly every state, an insurer can use medical underwriting to review your health history, deny your application, or charge a higher premium based on what it finds (5) . A handful of states go further than federal law requires. New York and Connecticut don't allow medical underwriting for Medigap at any time. Massachusetts holds an annual guaranteed-issue window each year from February 1 through March 31. And starting in 2026, Minnesota created a one-time guaranteed-issue window for people between 65 and 70 during the fall Medicare open enrollment period or the Medicare Advantage open enrollment period, though anyone who uses it pays a higher premium than someone who enrolled during their original window (5) . Outside of situations like these, the general rule holds. Enrolling during your initial six-month window , while you're guaranteed a policy regardless of your health, is almost always the better position to be in. Does it matter which state you live in beyond enrollment timing? Beyond those three, 16 states currently offer some version of a birthday rule, a limited annual window around your birthday when you can switch to a different plan with equal or lesser benefits without going through medical underwriting again (5) . The details vary widely. California and Oregon let you switch to any insurer during your window, while Illinois restricts the birthday rule to your current insurer or its affiliates and only applies between ages 65 and 75 (5) . If you're not sure whether your state has one, your State Health Insurance Assistance Program can tell you. Can you have Medigap and Medicare Advantage at the same time? No. It's illegal for anyone to sell you a Medigap policy if you're enrolled in a Medicare Advantage plan (4) . The two products work with different parts of Medicare. Medigap supplements Original Medicare's Part A and Part B, while Medicare Advantage replaces Original Medicare with a private plan that already includes its own cost-sharing structure. If you're comparing the two, that's a decision about which system you want to be in, not a question of adding one on top of the other. Where do people usually go wrong? Assuming a higher letter always means better coverage. The letters aren't ranked by quality. Plan N, for example, can be a smart choice for someone who rarely visits a doctor and would rather pay a small copay per visit than a higher monthly premium for coverage they mostly won't use. Waiting past the six-month enrollment window because they feel healthy. Guaranteed issue exists precisely because health can change quickly. Once that window closes, a new diagnosis between now and when you eventually apply could mean a denied application or a much higher premium. Assuming Plan F or Plan C are still an option. Both are closed to anyone who became newly eligible for Medicare on or after January 1, 2020. Only those who had Medicare before that date can still purchase or keep one. Buying the first quote instead of comparing insurers. Because the benefits are standardized by letter, the only real variable left is price, and that price can differ by hundreds of dollars a month between companies offering the identical plan. Comparing Medigap quotes across multiple insurers, ideally before your six-month enrollment window closes, is the most reliable way to find identical coverage at a lower price. References 1. Centers for Medicare & Medicaid Services. "2026 Medicare Parts A & B Premiums and Deductibles." Fact sheet, Nov. 14, 2025. https://www.cms.gov/newsroom/fact-sheets/2026-medicare-parts-b-premiums-deductibles 2. Medicare.gov. "Compare Medigap Plan Benefits." https://www.medicare.gov/health-drug-plans/medigap/basics/compare-plan-benefits 3. KFF (Kaiser Family Foundation). "Key Facts About Medigap Enrollment and Premiums for Medicare Beneficiaries." https://www.kff.org/medicare/key-facts-about-medigap-enrollment-and-premiums-for-medicare-beneficiaries/ 4. Medicare.gov. "Get ready to buy" and "When can I buy a Medigap policy?" https://www.medicare.gov/health-drug-plans/medigap/ready-to-buy 5. medicareresources.org. "Is there a best time to enroll in a Medicare supplement plan?" By Louise Norris, updated Sept. 6, 2026, citing Medicare.gov and Minnesota Statute. https://www.medicareresources.org/faqs/is-there-a-best-time-to-enroll-in-a-medicare-supplement-plan/ Premium and cost-sharing figures reflect 2026 rules and are indexed annually; confirm current figures before making a purchasing decision. This article is educational and does not constitute insurance, legal, or financial advice. Medicare/Insurance disclaimer: Medicare plan availability and costs vary by location. Contact a licensed Medicare advisor or visit Medicare.gov to compare plans available in your area. Affiliate disclosure: Greensprout is an independent, advertising-supported publisher and comparison resource. We may earn compensation when you click on links to products from our partners. This does not affect our editorial standards or recommendations.
