If you have Original Medicare and you’ve received a bill for thousands of dollars after a hospital stay, you already know the problem. Medicare Part A and Part B were never designed to cover everything. The deductibles, coinsurance, and copayments left behind — often called the “gaps” — can run into the tens of thousands of dollars in a single year for someone with a serious illness. That’s exactly the problem Medicare Supplement insurance, officially called Medigap, was created to solve.
In 2025, more than 14 million Americans carry a Medigap policy alongside their Original Medicare coverage. But with 10 standardized plan types available and dozens of insurance companies competing for your business, choosing the right Medicare supplement plan is one of the most financially significant decisions a retiree makes. This guide breaks down everything you need to know — including real 2025 costs, which plan most people choose, and the one enrollment mistake that could cost you hundreds of dollars a month for the rest of your life.
What Is Medicare Supplement Insurance (Medigap)?
Medicare Supplement insurance is private insurance you purchase to work alongside Original Medicare Parts A and B. These plans help pay for some out-of-pocket medical costs that are not covered under original Medicare, and you must have both Medicare Part A and Medicare Part B to apply for a Medigap plan. Medicare
Think of Medigap as a secondary payer. When you receive medical care, Medicare pays its share first, and your Medigap plan covers some or all of what remains — depending on the plan you selected. The Medicare Supplement plans that are available to you depend on the plans offered by companies in the state in which you live. Medicare
One critical rule beginners often miss: Medigap plans cannot be used with Medicare Advantage plans. Medicare If you’re enrolled in a Medicare Advantage plan (Part C), you cannot simultaneously carry a Medigap policy.
How Much Does Medigap Cost in 2025?
Cost is the first thing most people ask about, and the honest answer is that it varies significantly. Monthly premiums range from as little as $32 per month for certain high-deductible options to about $550 per month for the most comprehensive coverage, according to 2025 data from Humana. On average, beneficiaries pay between $90 and $300 per month for mid-level plans like Medicare Plan G or Plan N. Medicare
Medicare Supplement costs average $189 monthly at age 65, increasing to $238 by age 75. Comparing multiple insurers during Open Enrollment can save you $50 to $100 monthly on identical coverage. U.S. News & World Report
Here’s a quick breakdown of average monthly premiums for the most popular plans in 2025:
| Plan | Average Monthly Cost | Best For |
|---|---|---|
| Plan G | $142–$180/month | Most new enrollees |
| Plan N | $112–$140/month | Healthy seniors who rarely visit doctors |
| Plan F | $185–$228/month | Those eligible before Jan 1, 2020 only |
| High-Deductible Plan G | ~$58/month | Very healthy seniors willing to accept risk |
Source: CBS News, MedicareSupplement.com
Location makes a dramatic difference. Where you live has a massive impact on what you’ll pay — premiums can vary by more than $190 monthly for the same coverage. New York leads at $354 per month for both ages, while South Carolina and New Mexico offer the lowest rates at $160 for 65-year-olds. U.S. News & World Report
The 10 Medigap Plans: What Each One Covers
Medigap plans are administered by private insurance companies and come in 10 letter designations: A through D; F; G; and K through N. All plans with the same letter have the same coverage, but prices can vary based on the insurance company. Onealinsurancegroup
Here’s what the most important plans cover after Original Medicare pays its share:
Plan G covers: Part A coinsurance and hospital costs, Part B coinsurance and copayments, blood (first 3 pints), Part A hospice care coinsurance, skilled nursing facility coinsurance, Part A deductible, Part B excess charges, and 80% of foreign travel emergency care. The only gap it leaves is the Part B deductible.
Plan N covers everything Plan G covers except Part B excess charges, and requires copays of up to $20 for office visits and up to $50 for emergency room visits that don’t result in hospital admission.
Plan F covers everything including the Part B deductible — but Plan F is only available to those who became Medicare-eligible before January 1, 2020. Medicare Guide
Plans K and L are cost-sharing plans with lower premiums but out-of-pocket limits. The 2025 out-of-pocket maximum is $7,220 for Plan K and $3,610 for Plan L. Medicare
For official plan benefit comparisons, see: Medicare.gov — Compare Medigap Plan Benefits
Medicare Supplement Plan G: The Most Popular Choice in 2025
Plan G has become the dominant Medigap plan for new Medicare enrollees, and for good reason. 39% of Medicare Supplement beneficiaries now have Plan G, and the average premium for Plan G in 2025 was roughly $155.33 per month, or $1,864 per year. NerdWallet
Plan G offers some of the most comprehensive coverage available today, filling in most gaps left by Original Medicare. After you pay your Part B deductible, the plan takes care of the rest. Your only other expense for the year would be the monthly premiums, making it a straightforward and predictable option. UnitedHealthcare
The only out-of-pocket cost you’ll face with Plan G is the Part B deductible, which is $257 in 2025. Onealinsurancegroup Once you’ve paid that amount, Plan G covers 100% of Medicare-approved costs for the rest of the year — no surprise bills, no additional copays.
Plan G also has a high-deductible version. In 2025, the average monthly premium for a High-Deductible Plan G was $57.92 or $695 per year. The high-deductible amount for 2025 is $2,870 — meaning you pay the first $2,870 of covered costs before the plan kicks in. NerdWallet This makes sense only for people in excellent health who want catastrophic protection at a very low monthly cost.
External Resource: NerdWallet — Best Medigap Insurance Companies 2025
Medicare Supplement Plan N: The Budget-Friendly Runner-Up
Plan N has grown in popularity among seniors who are generally healthy and want solid coverage with meaningfully lower premiums. Plan N averages $112–$140 per month — lower premiums than Plan G or Plan F, but you may pay up to $20 copays for some doctor visits and up to $50 for ER visits that don’t result in admission. Medicare Interactive
The other key difference: Plan N doesn’t cover Medicare Part B excess charges — charges by doctors who don’t accept the full Medicare-approved amount as full payment. These doctors can charge you up to 15% over the Medicare-approved amount for services. Medicare Guide However, excess charges are relatively rare in practice, and several states including Connecticut, Massachusetts, Minnesota, New York, Ohio, Pennsylvania, Rhode Island, and Vermont have banned excess charges entirely. Onealinsurancegroup If you live in one of these states, Plan N becomes significantly more attractive.
When Plan N makes more sense than Plan G:
- You’re in good health and see a doctor fewer than 6–8 times per year
- You live in a state that bans excess charges
- The premium difference in your area is $40 or more per month
- You’d rather bank the savings and pay copays as needed
External Resource: Kiplinger — What’s the Best Medigap Plan?
Plan G vs. Plan N: Which One Wins in 2025?
This is the comparison most new enrollees need to make. Both plans provide excellent coverage — the decision comes down to math and personal preference.
In some areas, the savings with Plan N might be substantial enough to make the extra co-pays and the small risk of excess charges worth it. In other states, the difference in premiums might be so small that you’d rather pay a bit more each month to get the all-encompassing coverage that Plan G provides. UnitedHealthcare
Run the numbers before you decide. If Plan G costs $160/month and Plan N costs $125/month in your area, Plan N saves you $35/month or $420/year. If you make 10 doctor visits a year at $20 each, that’s $200 in copays. You’d still come out $220 ahead with Plan N. But if you visit the doctor frequently or have ongoing health conditions, Plan G’s flat-rate predictability is worth every penny.
Plan F: Still the Gold Standard — If You Qualify
Plan F offers more benefits than any other plan type and covers most out-of-pocket costs for Part A and Part B — but it’s not an option for new Medicare members. Medicare Guide If you became eligible for Medicare before January 1, 2020 and haven’t yet enrolled in a Medigap plan, Plan F is worth pricing out. It covers 100% of everything including the Part B deductible, meaning virtually zero out-of-pocket medical costs once enrolled.
Plan F averages $185–$228 per month and about 36% of Medigap enrollees carry Plan F. Medicare Interactive Many current Plan F holders keep their policy for the zero-hassle experience it provides, even if Plan G might have saved them money annually.
Medicare Supplement vs. Medicare Advantage: The Critical Decision
Before committing to Medigap, you need to understand the alternative. Medicare Advantage (Part C) is not supplemental insurance — it replaces Original Medicare entirely.
The monthly premiums for Medigap plans may be higher than Medicare Advantage plans, but they offer more predictable out-of-pocket costs, making it easier to budget for overall health care costs. Medicare Advantage plans generally have lower monthly premiums but include copayments, coinsurance, and deductibles that can vary significantly depending on the plan. Medicare
The key tradeoff: Medicare Advantage often costs less monthly but can cost far more when you actually use healthcare. Medigap costs more monthly but nearly eliminates financial surprises. For retirees on fixed incomes who value predictability — and especially for those with ongoing health conditions — Medigap generally offers superior financial protection.
External Resource: Medicare.gov — Official Plan Comparison Tool
The One Enrollment Rule That Could Cost You Thousands
The single most important thing to know about Medigap is the Open Enrollment Period (OEP).
The best time to enroll in Plan G is during your Medigap Open Enrollment Period, which lasts for six months starting the month you are both 65 and enrolled in Medicare Part B. During the OEP, healthy people and those with health conditions pay the same premium — insurers cannot deny you coverage or charge higher rates due to health conditions. Kiplinger
If you apply outside this window, insurers can use medical underwriting, which may result in higher premiums or even denial of coverage. Kiplinger
This is not a technicality — it’s the difference between being able to get comprehensive coverage at standard rates versus potentially being denied entirely because of a pre-existing condition. Enrolling when you’re first eligible during the Medigap Open Enrollment Period means insurers generally cannot deny you coverage or charge more because of pre-existing health conditions. Delaying can lead to underwriting, which often means higher premiums. Medicare
How to Get the Lowest Medigap Premium
Because the benefits in each lettered plan are exactly the same no matter which insurance company sells it, the premium is the only difference between policies with the same plan letter sold by different companies — and there can be big differences in those premiums. UnitedHealthcare
Strategies to lower your cost:
Compare multiple insurers. Rates for identical coverage can differ by hundreds of dollars between companies. U.S. News & World Report Get quotes from at least 3–5 carriers before enrolling.
Ask about discounts. Some insurers give price breaks for non-smokers, for paying annually instead of monthly, for being a member of certain organizations, or for combining multiple policies. Medicare
Understand premium rating methods. Community-rated policies charge everyone the same premium regardless of age. Issue-age-rated policies base premiums on your age at purchase and won’t increase due to aging. Attained-age-rated policies start cheaper but increase as you get older. Medicare Interactive Over a 20-year retirement, attained-age pricing can end up being significantly more expensive despite lower starting premiums.
Consider high-deductible Plan G if you’re in excellent health and have savings to cover the deductible. The $57.92/month average premium versus $155/month for standard Plan G is a massive difference.
FAQ: Medicare Supplement Plans 2025
Can I switch Medigap plans after I enroll? Yes, but outside your Open Enrollment Period you’ll likely face medical underwriting. Some states like California and Maine allow annual switching without health questions. Check your state’s specific rules.
Does Medigap cover prescription drugs? No. Medigap plans don’t include prescription drug coverage — you’ll need a separate Medicare Part D plan, which costs between $20 and $80 per month depending on your plan and location. U.S. News & World Report
Does Medigap cover dental, vision, or hearing? No. Original Medicare and Medigap both exclude routine dental, vision, and hearing care. You’ll need separate supplemental coverage for those services.
Can I use my Medigap plan anywhere in the country? Doctors and other healthcare providers must accept a Medigap plan if they accept Original Medicare, and Medicare beneficiaries can use their plan across the U.S. since Medigap plans do not have network limitations. Medicare This is one of Medigap’s biggest advantages over Medicare Advantage.
What if I move to a different state? Your Medigap policy follows you. Since benefits are federally standardized, a Plan G in Florida provides identical coverage to a Plan G in Texas. Your premium may change based on the new state’s rate environment.
Bottom Line: Which Medicare Supplement Plan Should You Choose?
For most people turning 65 today, Plan G is the strongest choice — comprehensive coverage, predictable costs, and the most popular plan among new enrollees for good reason. If you’re in excellent health and comfortable with small copays, Plan N saves meaningful money and makes particular sense in states that ban excess charges. If you became Medicare-eligible before 2020, get a quote for Plan F to see if it’s worth the higher premium for total peace of mind.
Whatever plan you choose, the single most important action is enrolling during your 6-month Open Enrollment Period. Missing that window can cost you in higher premiums — or coverage denial — for the rest of your life.
Official Resources:
- Medicare.gov — Compare Medigap Plans
- Medicare.gov — Find Plans in Your Area
- Official CMS Medigap Guide (PDF)
Further Reading:
- NerdWallet — Best Medicare Supplement Companies
- Kiplinger — What’s the Best Medigap Plan?
- U.S. News — Best Medicare Supplement Plans
- Boomer Benefits — Medicare Plan G Explained
Disclaimer: This article is for informational purposes only and does not constitute financial or insurance advice. Medicare rules, premiums, and deductibles change annually. Always verify current figures at Medicare.gov or consult a licensed Medicare insurance agent before making enrollment decisions.
