If you have Original Medicare (Parts A and B), you’ve probably heard about Medigap — also called Medicare Supplement Insurance. These private plans pay the share of your medical bills that Original Medicare doesn’t cover, like deductibles, coinsurance, and copays. For many people, a Medigap plan is the difference between predictable healthcare costs and unlimited financial exposure. Here’s how Medigap works, what each plan covers, and how to choose one without overpaying.
What Medigap actually does
Original Medicare is generous but incomplete. Part A covers hospital stays but has a deductible (about $1,676 per benefit period in 2026) and daily copays for long stays. Part B covers doctor visits and outpatient care but only pays 80% of approved charges — you owe the other 20%, and there’s no annual cap. A serious illness on Original Medicare alone could cost $30,000 or $50,000 out of pocket.
Medigap fills those gaps. After Medicare pays its share, your Medigap plan picks up most or all of what’s left, depending on which plan you choose. With a comprehensive Medigap plan, your out-of-pocket exposure can drop to near zero, no matter how serious the medical event.
Medigap plans are standardized
Here’s what makes Medigap unusual: the federal government standardizes the benefits. Plan G from one insurer covers exactly the same things as Plan G from any other insurer. The only thing that varies is the price — which can vary a lot.
Plans are labeled with letters: A, B, C, D, F, G, K, L, M, and N. Most enrollees today choose Plan G or Plan N. (Plans C and F are still available to people who became eligible for Medicare before January 1, 2020 — they’re no longer sold to newly eligible beneficiaries.)
What each plan covers
- Plan G — the most popular for new enrollees. Covers everything Original Medicare leaves except the Part B deductible (~$257/year in 2026). After you pay that deductible, your medical costs for the year are typically covered in full.
- Plan N — lower premium than G in most states. You pay the Part B deductible, plus small copays for office visits ($20) and ER visits ($50, waived if admitted), and you’re responsible for any “excess charges” (rare).
- Plan F — the most comprehensive, but only available if you became Medicare-eligible before 1/1/2020. Covers everything — including the Part B deductible — but premiums are typically the highest.
- High-Deductible Plan G — same coverage as G after you meet a $2,800 deductible (2026); much lower premiums; good for healthy enrollees who want catastrophic protection only.
- Plans K and L — lower premiums; you pay coinsurance up to an annual out-of-pocket maximum, then plan covers 100%.
- Plans A, B, D, M — less commonly chosen; varying combinations of partial coverage.
Why pricing varies so much
Although Plan G is identical at every insurer, premium quotes for the same person, same plan, same ZIP code can differ by hundreds of dollars per year between carriers. A 67-year-old in Ohio might find Plan G priced at $130/month at one insurer and $230/month at another — for the exact same benefits.
There are three reasons:
- Different actuarial assumptions. Insurers price based on their own claims experience and expected future costs.
- Different rating methods. Some states allow age-based pricing (premiums rise as you age); others require community rating (everyone pays the same).
- Marketing and overhead. Some carriers spend heavily on advertising or commissions, baked into premium.
This means shopping matters. Always get quotes from multiple insurers before choosing — and re-shop every few years, since premiums change.
The protected enrollment window
This is the most important Medigap rule to understand: you have a one-time, six-month protected enrollment window when you’re first eligible. It starts the month your Part B becomes effective and you’re 65 or older.
During this window:
- Insurers must sell you any Medigap plan they offer in your state
- They cannot use your health to deny you, charge you more, or impose waiting periods
- Pre-existing conditions cannot be excluded (with rare exceptions if you had less than 6 months of prior coverage)
After the window closes, in most states insurers can underwrite you — meaning they can ask about your health, decline to cover you, charge more, or impose waiting periods on pre-existing conditions. Only a handful of states (Connecticut, Massachusetts, Maine, New York, and a few others with limited rules) offer year-round Medigap protections.
Why this matters for the Medicare Advantage decision
If you choose Medicare Advantage at 65 and later decide you want to switch to Original Medicare with a Medigap plan, your protected window may already be closed. If your health has changed in the meantime — even slightly — you may find yourself unable to qualify for affordable Medigap coverage at all.
This is why some advisors recommend starting with Original + Medigap if you’re uncertain. You can always switch to Medicare Advantage later, but the door back to Medigap may not stay open.
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How rate increases work
Medigap premiums increase over time. Insurers use one of three rating methods, set by state law:
Community-rated (no-age-rated)
Everyone in your state pays the same premium regardless of age. Common in states like New York, Vermont, and a few others. Premiums still rise over time due to inflation and claims trends, but not because you got older.
Issue-age-rated
Premium is set based on your age when you first enroll. If you enroll at 65, you keep paying the “age 65 rate” (with general inflation increases). Most middle ground.
Attained-age-rated
Premium increases each year based on your current age. Cheap at 65, expensive at 80. Most common method nationally.
Attained-age-rated plans look like the best deal at 65 but can become very expensive in your late 70s and 80s — sometimes 50–100% higher than at enrollment. Issue-age and community-rated plans cost more upfront but are more stable long-term.
Medigap doesn’t include drugs
Medigap plans do not cover prescription drugs. (A few legacy plans pre-2006 did, but those plans were discontinued.) If you’re on Original Medicare with Medigap, you also need a separate Part D drug plan to avoid the late enrollment penalty and to have prescription coverage.
This is different from Medicare Advantage, where most plans bundle Part D into the same policy. With Original + Medigap + Part D, you have three separate policies, three separate premiums, and three separate cards — but each component can be optimized independently.
Real-world cost example
Take a 67-year-old retiree in Ohio choosing Plan G:
- Part B premium: $185/month (standard 2026)
- Plan G premium: $145/month (mid-range Ohio quote)
- Part D premium: $40/month
- Total monthly: $370
- Annual premium total: $4,440
- Plus Part B deductible: $257/year (one time)
- Maximum likely out-of-pocket: $4,697/year — with virtually all medical costs covered after the deductible
Compare that to a $0 premium Medicare Advantage plan with a $7,500 in-network out-of-pocket maximum. If our retiree stays healthy, Advantage could be cheaper. If she has a heart attack or cancer treatment, Plan G almost certainly costs less because the worst-case ceiling is much lower.
Common mistakes
- Buying from the first insurer that calls. Plan G is identical — never accept the first quote. Get at least 3 quotes from different carriers.
- Choosing Plan F at 65 (when available). Plan F was deprecated for new enrollees in 2020, but if you’re grandfathered, F often costs significantly more than G for only minor extra coverage. The math usually favors G.
- Picking attained-age-rated for the cheapest premium. The premium will rise every year. By age 80, that “cheap” plan may be one of the most expensive options.
- Skipping Part D because Medigap is comprehensive. Medigap doesn’t cover drugs. You still need a Part D plan or you’ll face a permanent late enrollment penalty.
- Not re-shopping every few years. Premiums change. Insurers raise rates differently. The cheap plan from 5 years ago may now be uncompetitive.
- Letting the protected enrollment window close without acting. If you’re leaning toward Original Medicare, enroll in Medigap during your 6-month window even if you’re tempted to wait.
Who Medigap usually fits
Medigap with Original Medicare tends to work well for:
- People who want predictable, low out-of-pocket costs even in worst-case medical years
- People with chronic conditions or who expect frequent specialist care
- People who travel often or split time between states
- People who value the freedom to see any Medicare-accepting provider without referrals or prior authorization
- People who can afford the higher monthly premiums in exchange for security
It tends to fit less well for healthy people on tight cash-flow budgets who would rather pay variable copays as they go than commit to higher fixed premiums.
How to choose your plan
- Decide on plan type — Plan G is the modern default; Plan N if you want lower premium and don’t mind small copays
- Get quotes from at least 3–5 insurers in your state for the same plan letter
- Check the rating method (attained-age vs. issue-age vs. community-rated) and ask about projected rate increases
- Verify the insurer’s financial strength rating (A.M. Best A or higher)
- Choose the lowest-priced reputable insurer for your selected plan letter
- Enroll during your 6-month protected window starting the month Part B begins
- Enroll in a Part D drug plan at the same time to avoid the late enrollment penalty
Free help is available: SHIP counselors (your state health insurance assistance program) can help compare plans, and licensed Medicare advisors can pull quotes from multiple insurers at once.
The bottom line
Medigap turns Original Medicare from “Medicare pays 80%, you owe the rest” into a system with predictable, comprehensive coverage. Plans are standardized so the only meaningful differences between insurers are price and customer service. Shop carefully, enroll during your protected window, pair with Part D, and re-shop every few years to keep your premium competitive.
If you value predictability, freedom to choose providers, and protection against catastrophic medical costs, Medigap is the system most retirees with the means choose — and many of those who skip it at 65 wish they had enrolled when they had the chance.
🆓 Ready to find the right Medigap plan?
Pricing varies dramatically between insurers for the exact same coverage. Our partner Chapter Medicare offers free one-on-one help from licensed advisors who can compare Medigap quotes in your area.
📞 Call 615-639-1937 | 🔗 askchapter.org/money
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Disclosure: We may receive a referral from Chapter if you choose to use their service. Chapter is a licensed health insurance agency and is not affiliated with or endorsed by Medicare or any government agency.
Further Reading
- Medicare Advantage vs. Original Medicare
- Medicare Parts A, B, C, and D Explained
- Medicare Costs and Premiums
- Medicare Enrollment
- Medicare Special Enrollment Periods
This article is for general educational purposes only and does not constitute insurance or financial advice. Visit medicare.gov or consult a licensed advisor for guidance specific to your situation.