Medicare Supplement Plans Cover the Gaps That Original Medicare Leaves

A Medicare Supplement plan (also called Medigap) pays for costs that Original Medicare does not. Original Medicare covers hospital stays and doctor visits, but leaves you responsible for deductibles, copayments, and coinsurance. A Medigap plan steps in to pay some or all of those out-of-pocket costs. The specific coverage depends on which plan letter you choose — Plan A, Plan B, Plan G, and others each cover a different combination of expenses.

Medigap is sold by private insurance companies, not by Medicare itself. You buy it as a separate policy to work alongside Original Medicare (Part A and Part B). It does not replace Original Medicare; it supplements it. You keep your Medicare card and use it the same way, but your Medigap plan pays the bills that Medicare does not.

Key Takeaways

  • Medicare Supplement plans pay deductibles, copayments, and coinsurance that Original Medicare requires you to pay out of pocket.
  • Different plan letters (A, B, D, G, K, L, M, N) cover different combinations of costs, so comparing what each covers is essential before you buy.
  • Medigap does not cover dental, vision, hearing aids, or long-term care — you need separate coverage for those.
  • You can only buy a Medigap plan if you have Original Medicare (Part A and Part B); you cannot use it with Medicare Advantage.
  • The best time to buy is during your open enrollment period, when insurers cannot deny you or charge more based on health history.

What Costs Medigap Plans Actually Pay

The most common expenses Medigap covers are the Part A deductible (the amount you pay before Medicare hospital coverage starts), the Part B deductible (for doctor and outpatient services), and coinsurance for hospital stays. Plan G, one of the most popular choices, covers all of these. It also pays the Part B excess charge — the amount a doctor can bill you above what Medicare allows, up to 15 percent in most states.

Many plans also cover some or all of your copayments for doctor visits and emergency room visits. Plan A covers copayments for emergency room visits and some hospital costs. Plan N covers copayments for doctor visits and emergency room visits, though you may pay a small copay for each visit. The exact copayment amounts vary by plan and by insurance company.

A few plans cover a portion of your prescription drug costs, though this is limited. Plan H, I, and J (which are no longer sold to new people but still exist for those who bought them before 2006) included some drug coverage. Current plans do not. If you need prescription drug coverage, you must buy a separate Part D plan.

What Medigap Plans Do Not Cover

Medigap does not cover dental work, vision care, hearing aids, or routine foot care. It does not cover long-term care (nursing home or in-home care for chronic conditions). It does not cover routine physical exams, eyeglasses, or hearing tests. If you need these services, you must pay out of pocket or buy separate coverage through a dental, vision, or hearing plan.

Medigap also does not cover care outside the United States, except in limited circumstances during travel. If you plan to travel internationally and want coverage, you need to check your specific plan's rules or buy a travel insurance policy. Original Medicare itself does not cover care outside the U.S., so Medigap cannot fill that gap.

Finally, Medigap does not cover services that Original Medicare does not cover. If Medicare says a treatment is not medically necessary, your Medigap plan will not pay for it either. Your Medigap plan works only for services that Medicare approves.

How to Compare the Different Medigap Plan Letters

There are ten standardized Medigap plans available in most states: A, B, D, G, K, L, M, and N. (Plans C and F are no longer sold to new people as of 2020.) Each plan letter covers the same benefits across all insurance companies — Plan G from one company covers the same things as Plan G from another company. The price differs, but the coverage does not.

The main differences are which deductibles and copayments each plan covers. Plan A is the most basic and least expensive; it covers fewer costs than Plan G. Plan G covers more costs and costs more in monthly premiums. Plans K and L cover a percentage of costs rather than all costs, which means you still pay some coinsurance even after your Medigap plan pays its share. Plan N has lower premiums but requires you to pay copayments for some doctor visits and emergency room visits.

To decide which plan makes sense for you, list the costs you expect to pay most often — doctor visits, hospital stays, or specialist visits — and see which plan covers those costs most completely. A plan with a higher monthly premium may save you money overall if you use healthcare frequently. A plan with a lower premium may be better if you rarely see doctors.

When You Can Buy a Medigap Plan and at What Cost

The best time to buy Medigap is during your open enrollment period, which lasts six months starting the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies must sell you any plan you want and cannot charge you more or deny you based on your health history. This protection is called may provide issue.

If you miss your open enrollment period, you can still buy a Medigap plan, but the rules change. Insurance companies can deny you, charge you more, or exclude coverage for pre-existing conditions. Some states have additional protections that extend may provide issue rights, but these vary. The safest approach is to buy during your open enrollment period.

Premiums vary by insurance company, by plan letter, and by your age and location. The same Plan G costs different amounts from different insurers in the same city. Shopping around by calling three to five insurance companies or using the Medicare Plan Finder tool on Medicare.gov can save you hundreds of dollars per year. Premiums also increase as you age, though the rate of increase depends on the insurance company's pricing method.

Medigap vs. Medicare Advantage: Which Covers More

Medicare Advantage (Part C) is a different type of coverage that replaces Original Medicare entirely. You cannot have both Original Medicare and Medicare Advantage at the same time, and you cannot buy a Medigap plan if you have Medicare Advantage. The two are mutually exclusive.

Medigap works best if you want to keep Original Medicare and have a plan that covers the gaps. Medicare Advantage works best if you want lower monthly premiums and do not mind using a network of doctors and hospitals. Medicare Advantage often includes dental, vision, and hearing coverage that Medigap does not, but it also has network restrictions and may require prior authorization for some services.

If you have Original Medicare and are considering whether to buy Medigap, the main question is whether you can afford the monthly premium. If you can, Medigap typically gives you more freedom to see any doctor who accepts Medicare, because you are not restricted to a network.

What to Ask Your Doctor and Insurance Company

Before you buy a Medigap plan, ask your current doctors whether they accept Medicare and whether they have any restrictions on Medigap patients. Most do, but it is worth confirming. Ask your insurance company what the exact copayments and coinsurance amounts are for the plan you are considering, because these vary by company even though the plan letter is the same.

If you take prescription medications, ask whether your Part D plan (which you buy separately) covers them, because Medigap does not cover drugs. If you need dental, vision, or hearing care, ask whether your Medigap plan covers any of these services — it does not, so you will need to budget for these separately or buy a separate plan.

If you are considering switching from one Medigap plan to another, ask your insurance company about the process and whether you will face any waiting periods or exclusions. If you are switching insurance companies, ask the new company whether they will waive any waiting periods for pre-existing conditions.

When to Seek Help Understanding Your Coverage

If you are confused about what your Medigap plan covers, call your insurance company's customer service number on your insurance card. They can tell you exactly what your plan pays for a specific service. You can also call Medicare at 1-800-MEDICARE (1-800-633-4227) to ask general questions about how Medigap works.

If you need help choosing a plan, your State Health Insurance information Program (SHIP) offers free counseling. To find your state's SHIP, visit shiptalk.org or call 1-877-839-2675. SHIP counselors can review your health needs and budget and recommend plans that might work for you.

If you receive a bill from a doctor or hospital that you think your Medigap plan should have paid, contact your insurance company first. If they deny the claim, ask why in writing and request an appeal. You have the right to challenge any claim denial.

Frequently Asked Questions

Can I use my Medigap plan at any hospital or doctor's office?

Yes, as long as the provider accepts Medicare. Medigap has no network restrictions — you can see any doctor or go to any hospital that accepts Medicare patients. This is one major advantage over Medicare Advantage, which limits you to in-network providers.

Do I need both a Medigap plan and a Part D prescription drug plan?

Yes, they cover different things. Medigap covers deductibles and copayments for medical services. Part D covers prescription medications. You buy them as separate policies. If you do not enroll in Part D when you first become may be able to access, you may pay a penalty if you join later.

What happens to my Medigap plan if I move to a different state?

Your plan may not be available in your new state, because Medigap plans vary by state. You will likely need to switch to a plan that is sold in your new state. Contact your insurance company at least 30 days before you move to ask about your options and whether you can switch without losing coverage.

Can I switch from one Medigap plan to another if my needs change?

Yes, but the rules depend on whether you are switching plans or insurance companies. If you switch to a different plan letter from the same company, you usually can. If you switch to a different insurance company, you may face medical underwriting or waiting periods unless you may have access to for may provide issue rights in your state.

Does Medigap cover care I receive while traveling outside the United States?

Standard Medigap plans do not cover care outside the U.S. Some plans offer limited emergency coverage during travel, but this is rare. If you travel internationally regularly, ask your insurance company whether your plan includes any international coverage, or consider buying a separate travel insurance policy.