What a Medicare Supplement Plan Does

A Medicare Supplement plan (also called Medigap) is insurance you buy from a private company to cover costs that Original Medicare leaves behind. Original Medicare covers hospital and doctor visits, but you still pay deductibles, copayments, and coinsurance. A Medigap plan fills those gaps—it pays some or all of those out-of-pocket costs.

When you're on SSDI and turn 65, you become may be able to access for Medicare automatically. At that point, you can choose to add a Medigap plan on top of Original Medicare. The Medigap plan doesn't replace Medicare; it works alongside it. You keep your Medicare card and your Medigap card, and you use both when you see a doctor or go to the hospital.

Medigap plans are standardized by the federal government, which means the same plan (like Plan G or Plan N) covers the same things no matter which insurance company sells it to you. The price varies by company and by where you live, but the coverage is identical.

Key Takeaways

  • Medigap plans cover deductibles and copayments that Original Medicare doesn't pay, reducing your out-of-pocket costs when you see a doctor or go to the hospital.
  • You can only buy a Medigap plan if you have Original Medicare (not Medicare Advantage), and you must be enrolled in both Medicare Part A and Part B.
  • The best time to buy Medigap is during your six-month open enrollment period, which starts the month you turn 65 and are enrolled in Medicare Part B—insurance companies cannot deny you or charge more during this window.
  • Plan G and Plan N are the most common choices; Plan G covers more costs but costs more per month, while Plan N has lower premiums but you pay more at the doctor's office.
  • Your SSDI income does not affect whether you can buy Medigap, but your monthly premium comes out of your own pocket and is not covered by any government program.

When You Can Buy a Medigap Plan

You can buy a Medigap plan only after you are enrolled in both Medicare Part A and Medicare Part B. If you're on SSDI, you become may be able to access for Medicare at 65, and Medicare Part A (hospital insurance) starts automatically. You must sign up for Part B (doctor and outpatient care) yourself, either when you turn 65 or during the General Enrollment Period if you miss the initial window.

The ideal time to buy Medigap is during your six-month open enrollment period, which begins the first day of the month you turn 65 and are enrolled in Part B. During these six months, insurance companies must sell you any Medigap plan you want at the standard price—they cannot refuse you, charge you more because of health problems, or exclude pre-existing conditions. After this window closes, insurance companies can deny you coverage or charge higher premiums based on your health history.

If you miss your open enrollment period, you can still buy Medigap later, but you may face medical underwriting (the company reviews your health) and higher costs. Some states have additional protections that extend enrollment windows, so check with your state insurance commissioner's office if you missed the federal important date.

The Difference Between Plan Types

Medigap plans are labeled A through N (and G and M in some states). Each letter represents a different combination of coverage. You do not choose what each plan covers—that is set by federal law. What you choose is which letter plan fits your budget and health needs.

Plan G is the most comprehensive option available to people new to Medicare. It covers your Part B deductible, coinsurance, copayments, and excess charges (if a doctor charges more than Medicare allows). You pay a monthly premium, usually between $100 and $250 depending on your age, location, and the insurance company, but your out-of-pocket costs at the doctor are minimal. Plan G does not cover your Part A deductible (hospital deductible), which is $1,676 in 2024, but that is a one-time cost per hospital stay.

Plan N costs less per month than Plan G—often $50 to $150—but you pay more when you use care. With Plan N, you pay up to $200 per doctor visit and up to $50 per emergency room visit (though the ER copay is waived if you are admitted to the hospital). You also pay your Part B deductible and coinsurance. Plan N makes sense if you are generally healthy and do not see doctors often.

Other plans (A, B, D, F, K, L, M) exist but are rarely sold to new customers. Your insurance agent can show you a comparison chart of all available plans in your area.

How Much Medigap Costs and What Affects the Price

Medigap premiums vary widely based on three main factors: the plan letter you choose, your age, and where you live. A Plan G might cost $120 per month in one state and $180 in another. The same plan costs more in New York than in Alabama, and costs more at age 75 than at age 65.

Insurance companies use one of three pricing methods: community-rated (everyone in your area pays the same regardless of age), age-rated (your premium increases as you age), or issue-age-rated (your premium is based on your age when you buy the plan and stays the same relative to others your age, but increases over time). You cannot control which method a company uses, but you can compare prices across companies. Calling three or four insurance companies for quotes takes about an hour and can save you hundreds of dollars per year.

Your SSDI benefit amount does not affect the price you pay for Medigap. The insurance company cannot charge you more because you receive disability benefits. However, the premium is your responsibility—it does not come out of your SSDI check automatically, and no government program pays it for you. You receive your SSDI payment, and you pay the Medigap premium separately to the insurance company.

Medigap Versus Medicare Advantage

When you turn 65 and enroll in Medicare, you have two paths: Original Medicare plus a Medigap plan, or Medicare Advantage (Part C). You cannot have both at the same time. Understanding the difference matters because it affects your costs and which doctors you can see.

Original Medicare plus Medigap lets you see any doctor or hospital in the country that accepts Medicare—there are no networks. You pay a monthly Medigap premium, and then you have predictable costs at the doctor's office. This is the path that requires a Medigap plan.

Medicare Advantage is an all-in-one plan run by a private insurance company. It includes hospital, doctor, and usually prescription drug coverage in one plan. Medicare Advantage plans often have $0 premiums (you pay only your Part B premium to Medicare), but they use networks, have copayments and deductibles, and may require prior approval from the insurance company before you see a specialist. You do not buy Medigap if you have Medicare Advantage; the two are mutually exclusive.

Neither path is universally better—it depends on your health, your doctors, and your budget. If you want to keep your current doctors and do not mind paying a monthly Medigap premium for predictable costs, Original Medicare plus Medigap is often the choice. If you want a low or zero premium and are willing to use a network, Medicare Advantage may work.

How to Compare and Buy a Medigap Plan

Start by deciding which plan letter appeals to you. If you want the lowest out-of-pocket costs and can afford a higher monthly premium, Plan G is standard. If you want a lower monthly premium and are comfortable with copayments at the doctor, Plan N is worth comparing.

Next, get quotes from at least three insurance companies. You can call companies directly, use the Medicare Plan Finder tool at Medicare.gov, or contact your state health insurance information program (SHIP), which offers free counseling. When you call, have your Medicare number ready and tell the company your age, the plan letter you want, and your zip code. They will quote you a monthly premium.

Compare the monthly premiums across companies. The coverage is identical (Plan G from Company A covers the same things as Plan G from Company B), so the lowest price is usually the best choice. Once you decide, you can buy the plan by phone, mail, or online through the insurance company's website. The plan typically starts on the first of the following month.

What Happens to Your Medigap Plan If Your Circumstances Change

If you move to a different state, your Medigap plan may not be available in your new state, or the same plan may be sold under different rules. You have the right to switch to a different Medigap plan in your new state without medical underwriting, but you must do so within 63 days of moving. Contact your current insurance company or a new company in your new state to arrange the switch.

If your income changes—for example, if you start working part-time or receive a cost-of-living increase in your SSDI—your Medigap premium does not change. Medigap premiums are based on age, location, and plan type, not on income. Your SSDI benefit amount has no effect on what you pay for Medigap.

If you become dissatisfied with your Medigap plan, you can switch to a different plan letter during the annual open enrollment period (October 15 to December 7 each year). Outside of open enrollment, switching may require medical underwriting. Your state may have additional switching rights; check with your state insurance commissioner's office.

Frequently Asked Questions

Can I have both Medigap and Medicare Advantage at the same time?

No. You must choose one or the other. If you have Medicare Advantage and want to switch to Original Medicare plus Medigap, you can do so during the annual open enrollment period (October 15 to December 7). If you switch, you have the right to buy a Medigap plan without medical underwriting, but only if you enroll in the Medigap plan within 63 days of dropping Medicare Advantage.

Does my SSDI pay for my Medigap premium?

No. Your SSDI benefit and your Medigap premium are separate. You receive your SSDI payment, and you pay the Medigap premium directly to the insurance company each month. The premium does not come out of your SSDI check unless you arrange automatic payments with the insurance company.

What if I cannot afford a Medigap plan?

If your income is very low, you may be may be able to access for Medicaid, which can help pay for Medicare costs including deductibles and copayments. Medicaid rules vary by state. Contact your state Medicaid office or call 1-800-MEDICARE to learn whether you may have access to. Some states also offer programs that help pay Medicare premiums for people with limited income.

Can an insurance company deny me Medigap coverage because of a pre-existing condition?

During your six-month open enrollment period (starting when you turn 65 and enroll in Part B), no. Insurance companies must sell you any Medigap plan you want at the standard price. After open enrollment ends, insurance companies can deny you or charge more based on health history. If you missed your window, contact your state insurance commissioner's office—some states have additional protections.

What is the difference between Plan G and Plan F?

Plan F is no longer sold to people new to Medicare as of January 1, 2020. If you enrolled in Plan F before that date, you can keep it. Plan G is the modern equivalent and covers nearly everything Plan F did, except Plan G does not cover your Part B deductible (currently $240 per year). For most people, Plan G is the better choice today.