What Is Medicare Supplement Insurance (Medigap)?
Published on July 21, 2026
Written By: Mark Prip
Medicare Supplement insurance (also called Medigap) is private insurance that works alongside Original Medicare (Part A and Part B) to help pay out-of-pocket costs such as deductibles, copayments, and coinsurance.
It isn't a replacement for Medicare, and it isn't the same thing as a Medicare Advantage plan — instead of adding new benefits, it simply picks up cost-sharing that Original Medicare leaves behind.
How Medigap Works With Original Medicare
Under Original Medicare, you're responsible for an annual deductible for Part A (hospitalization) and Part B (outpatient services and doctor visits).
After Medicare pays its share, you're still responsible for deductibles, coinsurance, copayments, and other cost-sharing depending on the type of care you receive. For Part B services, Medicare generally pays 80% of the Medicare-approved amount after you've met the Part B deductible.
Those out-of-pocket costs are often called the "gap" in Medicare coverage, and they can add up quickly if you have a serious illness or hospital stay. A Medigap policy is built to cover some or all of that gap, depending on the plan you choose.
Here's what that actually looks like in practice: say you need outpatient surgery, and after Medicare's discount the approved cost is $10,000.
If you've already met your Part B deductible for the year, Medicare pays 80% of that — $8,000 — and you're responsible for the remaining $2,000.
That $2,000 is the "gap." A Medigap plan is built specifically to pick up that kind of bill so it doesn't land on you.
Who Is Eligible for Medigap?
You become eligible for Medigap once you're age 65 and enrolled in Medicare Part B. Your six-month Medigap Open Enrollment period begins at that point, and it's the best time to apply — insurers can't deny you coverage or charge more based on your health during this window.
Apply outside that period, and an insurer can use medical underwriting to reject your application or raise your premium. Certain situations also give you guaranteed issue rights, allowing you to buy a Medigap policy without medical underwriting.
In plain terms, "medical underwriting" just means the insurance company can ask about your health history and use it to decide whether to cover you and what to charge — similar to how a life insurance company might ask questions before issuing a policy.
During your Open Enrollment window, they can't do that, no matter what health conditions you have. Miss that window, and something like a heart condition or recent surgery could mean a higher premium or even a denial.
"Guaranteed issue rights" is the safety net for that — certain events, like losing employer coverage or a plan leaving your area, force an insurer to cover you anyway, no health questions asked.
What Does Medicare Supplement Insurance Cover?
Depending on the plan you choose, Medigap can help pay for:
Medigap Can Help Pay For
- Part A hospital coinsurance (up to 365 extra days)
- Part B coinsurance
- Part A deductible
- Skilled nursing facility coinsurance
- Hospice coinsurance
- Blood (first 3 pints)
- Part B excess charges
- Foreign travel emergency care
Medigap Does Not Cover
- Vision care
- Dental care
- Hearing aids
- Eyeglasses
- Long-term nursing home care
- Private-duty nursing
- Prescription drugs (Part D)
- Cosmetic surgery
Medigap plans are standardized in 47 states, meaning a given plan letter — Plan G, for example — offers identical benefits no matter which insurer sells it or which of those 47 states you live in. See our full Medicare Supplement plans comparison chart for a side-by-side look at every letter. Massachusetts, Wisconsin, and Minnesota standardize their plans differently.
Think of it a bit like buying the same model of car from two different dealerships — a Plan G from Aetna covers exactly the same things as a Plan G from Mutual of Omaha.
The features don't change from company to company; only the price and the customer service do. That's good news for you — it means you can shop on price without worrying you're getting a "lesser" version of the plan.
What Types of Medicare Supplement Plans Are Available?
There are 12 standardized Medigap plans, labeled A through N, each covering a different combination of costs. In practice, most people choose from a small handful of plans that offer the best balance of coverage and price. Plan G, Plan N, and High-Deductible Plan G are the most commonly purchased today.
Plan G
Covers nearly everything Original Medicare doesn't, leaving only the Part B deductible for you to pay. The most complete plan available to people newly eligible for Medicare.
Plan N
Similar coverage to Plan G with a lower premium, in exchange for small copays (up to $20 for some office visits, up to $50 for certain ER visits).
High-Deductible Plan G
Same coverage as Plan G, but you cover your own share of Medicare-approved costs — coinsurance, copays, deductibles — up to $2,950 (2026) before the plan kicks in, in exchange for a much lower monthly premium.
One clarification: the $2,950 deductible applies to your share of Medicare-approved costs — not the full bill. Original Medicare keeps paying its normal share the whole time, deductible or not.
Example: on a $500 doctor visit, Medicare still pays its usual 80% after your Part B deductible, leaving you around $100 toward the $2,950. On a $3,000 hospital stay, you're only on the hook for the Part A deductible — not the full $3,000.
Once your own share adds up to $2,950 for the year, the plan starts covering 100% of what Plan G normally covers.
Medicare SELECT Plans
Medicare SELECT is a type of Medigap policy that requires you to use a provider network for certain non-emergency services. In exchange, premiums are often lower than standard Medigap plans. Not every state offers Medicare SELECT plans.
One term worth pausing on: "Part B excess charges." Most doctors agree to accept Medicare's approved payment amount in full — but a small share don't, and they're legally allowed to charge up to 15% more than that approved amount.
So if Medicare approves $200 for a visit, a doctor who doesn't "accept assignment" could bill you an extra $30 on top of it.
Plan G covers that extra amount; Plan N does not — which is one of the real trade-offs behind Plan N's lower premium. See our full Plan G vs. Plan N comparison for more.
How Much Does Medicare Supplement Insurance Cost?
Medigap premiums typically range from about $42 to $320 a month. As a rule, plans with more comprehensive coverage cost more, while plans that require copayments — like Plan N — trade a lower premium for some cost-sharing.
Because benefits are standardized, you're primarily paying for the insurance company — not additional coverage. That's why shopping for premiums is so important.
| Company | Plan | Lowest Rate | Highest Rate | Gender | State |
|---|---|---|---|---|---|
| Aetna | G | $186.68 | $232.31 | Male | TX |
| Mutual of Omaha | G | $117.38 | $132.37 | Female | OH |
| Aetna | G | $178.85 | $208.03 | Male | PA |
| United Healthcare | G | $173.20 | $279.14 | Female | CA |
| Florida Blue (FL residents only) | G | $230.64 | $258.48 | Male | FL |
Rates are subject to your Medicare Part B start date and/or medical underwriting.
Get Your Personalized Medigap QuoteWondering why there's a range instead of one number? The "lowest" and "highest" rates reflect that the same company's Plan G can cost different people different amounts, mainly based on age and where they live.
A 66-year-old in a lower-cost ZIP code might land near the low end; a 78-year-old in a higher-cost area might land near the top. It's the same coverage either way — the price simply reflects your own rating factors.
Several factors influence what you'll pay:
- Age
- Gender
- ZIP code
- Insurance company
- Benefit level (which plan you choose)
- Cost-sharing structure
- Household discounts
Your Medigap premium is on top of your monthly Medicare Part B premium.
Most Medigap plans also require you to pay your Part B deductible before benefits kick in — the exceptions being Plan F, High-Deductible Plan F, and Plan C, all limited to beneficiaries eligible for Medicare before January 1, 2020.
Is Medicare Supplement Insurance Worth It?
Yes — it's absolutely worth it, and I'd go further: picking up some form of Medicare Supplement coverage isn't optional if you want to protect yourself financially. (For a deeper look at this question, see Do I Really Need Supplemental Insurance With Medicare?)
Here's why that's not just an opinion. Original Medicare, by itself, has no out-of-pocket maximum. There is no dollar amount at which your 20% coinsurance stops.
A major surgery, a long hospital stay, a serious diagnosis — any of these can generate tens of thousands of dollars in coinsurance with Original Medicare alone, and every dollar of it is yours to pay. That's not a small gap in coverage. That's an open-ended financial risk sitting on top of your retirement.
Enrolling in any Medicare Supplement plan closes that risk. It doesn't matter which letter you choose — Plan G, Plan N, or a high-deductible option — every Medigap plan puts a ceiling on what a catastrophic health event can cost you. That's the whole point of this kind of insurance, and it's why I consider it a critical, not optional, part of a Medicare strategy.
What this looks like in practice: in a moderate year — a handful of doctor visits, some routine testing — you might generate around $5,000 in Medicare-approved charges. After your $283 Part B deductible, the 20% coinsurance on the rest comes to roughly $1,200 out of pocket for the year under Original Medicare alone.
A hospital stay is a different story. A serious surgery or extended hospitalization can easily involve $50,000 or more in Medicare-approved charges — and hospitals often bill far higher than that before Medicare's negotiated rate brings it down. On top of your Part B coinsurance, you'd also owe the $1,736 Part A deductible for the hospital stay itself. With Original Medicare alone, none of this has a ceiling.
With Plan G, your exposure in either scenario — the quiet year or the hospital stay — is capped at that same $283 Part B deductible. Nothing more.
Here's what that gap looks like at the extremes — a major surgery billed at $250,000, and a serious multi-day hospitalization billed at $1,000,000:
| Scenario | Total Billed Charges | Medicare-Approved Amount | Your Cost — Original Medicare Alone | Your Cost — Plan G |
|---|---|---|---|---|
| Major surgery / hospitalization | $250,000 | ~$45,000 | ~$10,962 | $283 |
| Extended or complex hospitalization | $1,000,000 | ~$120,000 | ~$25,962 | $283 |
These are illustrative estimates, not a quote — actual Medicare-approved amounts vary by procedure, provider, and location.
What This Means for You
I've worked with clients who split the year between two homes — say, half the year in one state and half in another — and Medigap just travels with them.
Because it works with any provider who accepts Medicare, you're never boxed into a network, and you can walk into a specialty facility anywhere in the country without checking whether it's "in-network" first. That's a level of freedom Medicare Advantage plans, with their networks and prior authorizations, generally can't match.
Freedom to choose your care
Medicare Supplement
- Any provider who accepts Medicare
- No referrals needed
- No prior authorizations
- Coverage travels nationwide
- Guaranteed renewable
Medicare Advantage
- Limited to plan network
- Referrals often required
- Prior authorizations common
- Coverage tied to service area
- Plans can change yearly
There's a Medigap plan for every budget, from the comprehensive Plan G down to the lower-premium, higher-cost-sharing options — but no matter which letter you choose, you get that same core benefit: freedom to see who you want, when you want, without a network or a referral standing in the way.
Who Should Consider Medigap?
Medigap tends to make the most sense if you:
- Want the freedom to see any provider who accepts Medicare, without referrals, prior authorizations, or network restrictions
- Split time between two residences or travel frequently and want coverage that goes with you
- Travel and want coverage for foreign travel emergencies
- Would rather pay a steady premium than risk large, unpredictable medical bills
- Have ongoing health needs where frequent doctor visits or procedures could add up under Original Medicare alone
- Want predictable healthcare expenses in retirement
Even if you're generally healthy today, I'd still urge you not to skip this decision — health can change quickly and without warning, and Original Medicare's uncapped coinsurance doesn't care how healthy you were last year.
The best time to lock in a Medigap plan is during your Open Enrollment Period, precisely because that's the one window where your current health can't be held against you. Waiting is the riskiest move you can make.
How to Apply for a Medicare Supplement Plan
The best time to apply for Medigap is during your six-month Open Enrollment Period, which starts once you're 65 and enrolled in Medicare Part B.
During this window, insurers must accept you regardless of any health conditions and can't charge you more because of them.
Apply outside this period, and insurers are generally allowed to use medical underwriting — they can charge higher premiums or deny coverage based on your health history.
Outside your Open Enrollment Period, you may still qualify for guaranteed issue rights after certain life events, allowing you to enroll without medical underwriting.
Once you're enrolled and paying your premium on time, Medigap policies are guaranteed renewable, meaning your coverage can't be canceled as long as you stay enrolled in Medicare Part B.
Ready to Learn More?
Medigap can provide valuable financial protection by limiting many of the out-of-pocket costs that Original Medicare doesn't cover. Because every company offers the same standardized benefits for the same plan letter, the most important differences are price, customer service, and available discounts. See our Top Medicare Supplement Companies review to compare multiple insurers before enrolling.
With Policy Guide's assistance, you'll have access to licensed agents who can help you compare plans, quotes, and policies so you can make an informed decision.
Mark Prip
Since 2003, Mark Prip has been leading Policy Guide, Inc., providing knowledgeable information about Medicare, life insurance, and dental coverage to clients in over forty states. With extensive hands-on experience helping Medicare beneficiaries understand and select health coverage, he brings decades of practical industry knowledge and client support. Mark has held his Florida Health & Life Insurance License (E051889) since 2003. View his license profile on the Florida Department of Financial Services website.