What Medicare Supplement Plans Do

A Medicare Supplement plan (also called Medigap) is insurance you buy from a private company to cover costs that Original Medicare leaves you paying out of pocket. Original Medicare covers a lot, but not everything — you still owe deductibles, copayments, and coinsurance. A Medigap plan fills those gaps by paying some or all of those amounts.

Medigap is different from Medicare Advantage. With Medigap, you keep Original Medicare (Parts A and B) and add a private plan on top. With Medicare Advantage, you replace Original Medicare with a private plan. This guide focuses on Medigap plans only.

You pay a monthly premium to the private insurance company for your Medigap plan, separate from your Medicare Part B premium. The amount varies by plan type, your age, where you live, and the insurance company you choose.

Key Takeaways

  • Medigap plans are sold by private insurance companies and work alongside Original Medicare to pay costs Medicare does not cover.
  • Ten standardized Medigap plans exist (labeled A through N), and each covers a different combination of deductibles, copayments, and coinsurance.
  • You can enroll in a Medigap plan during your Initial Enrollment Period (the six months after you turn 65 and enroll in Medicare Part B), when you have the strongest legal protection against being denied or charged more for pre-existing conditions.
  • Outside your Initial Enrollment Period, some states allow you to enroll in Medigap at any time, but others limit when you can join, and insurers can charge you more based on your health history.
  • Plan premiums differ by insurance company, age, and location, so comparing quotes from multiple insurers is worth doing before you choose.

The Ten Standardized Medigap Plans

Medicare sets the rules for what each Medigap plan must cover, so Plan A from one insurance company covers the same things as Plan A from another. The ten plans are labeled A, B, D, G, K, L, M, N, and two high-deductible versions of G and F. (Plan C and Plan F were discontinued for people who became may be able to access for Medicare after January 1, 2020.)

Plan G and Plan N are the most common choices for new enrollees because they offer broad coverage at a reasonable cost. Plan G covers your Part B coinsurance (the percentage you owe after Medicare pays its share), your Part A deductible, and most other out-of-pocket costs — but not your Part B deductible. Plan N is less expensive but requires you to pay a copayment when you visit the doctor or emergency room.

Plan A is the simplest and least expensive option. It covers your Part A deductible, Part A coinsurance, Part B coinsurance, and some other costs, but leaves you responsible for your Part B deductible (which is $240 in 2024, though this amount changes yearly).

Plans B, D, K, L, and M offer different combinations of coverage. A licensed insurance agent or your State Health Insurance information Program (SHIP) can walk you through what each plan covers and what you would still owe under each one, based on your own health and expected medical use.

When You Can Enroll and What Protection You Have

Your Initial Enrollment Period for Medigap runs for six months, starting the month you turn 65 and enroll in Medicare Part B. During this window, you have may provide issue rights — meaning an insurance company cannot deny you coverage, charge you more because of pre-existing conditions, or impose a waiting period before coverage starts.

If you enroll in a Medigap plan during your Initial Enrollment Period, coverage typically begins on the first day of the month after the insurance company receives your process and payment. This is the strongest legal protection you have, and it is why most people enroll during this time.

If you miss your Initial Enrollment Period, the rules depend on your state. Some states have open enrollment periods that allow you to enroll in any Medigap plan at any time without the insurance company checking your health. Other states limit when you can enroll — for example, only during a specific month each year, or only if you lose other coverage. Outside your Initial Enrollment Period and outside any state open enrollment period, an insurance company can deny you, charge you more, or exclude coverage for pre-existing conditions.

Check with your State Health Insurance information Program to learn the enrollment rules in your state. You can find your SHIP by calling 1-800-MEDICARE or visiting Medicare.gov.

How Medigap Premiums Work

Medigap premiums vary widely depending on three main factors: the plan you choose, your age, and where you live. The same plan from the same insurance company can cost different amounts in different states or even different counties.

Insurance companies use one of three methods to set premiums: community-rated (everyone in your area pays the same price regardless of age), issue-age-rated (your premium is based on your age when you enroll), or attained-age-rated (your premium increases as you get older). Attained-age-rated plans are usually cheaper when you first enroll but increase more over time. Issue-age-rated plans cost more upfront but increase more slowly. Community-rated plans do not change based on your age.

You should get quotes from at least three insurance companies before you choose. The same plan can cost hundreds of dollars more per year from one company than another. Medicare.gov has a tool to compare plans and premiums in your area, or you can call 1-800-MEDICARE to request a comparison.

What Medigap Does Not Cover

Medigap plans do not cover dental, vision, hearing aids, or long-term care. They also do not cover prescription drugs — you need a separate Part D plan for that. If you want dental or vision coverage, you would need to buy those separately from a private insurance company.

Medigap also does not cover care you receive outside the United States, except in limited situations. If you travel internationally, you may want to look into travel insurance or a plan that offers some foreign travel coverage.

Finally, Medigap does not cover costs related to care that Medicare itself does not cover. For example, if Medicare does not cover a particular treatment or procedure, your Medigap plan will not cover it either.

Changing Plans or Switching Insurance Companies

You can switch from one Medigap plan to another or change insurance companies, but the rules depend on whether you are still in your Initial Enrollment Period. During your Initial Enrollment Period, you have may provide issue rights and can switch plans without the insurance company checking your health.

After your Initial Enrollment Period ends, your ability to switch depends on your state's rules. Some states allow you to switch at any time. Others limit switches to specific times of year or only if you have a may have access to life event (such as moving out of state or losing employer coverage). If you switch outside a protected time, the new insurance company can charge you more or deny you based on your health history.

Before you switch, make sure your new plan starts before your old plan ends, so you do not have a gap in coverage. Contact both the old and new insurance company to confirm the timing.

Questions to Ask Your Doctor or Insurance Company

Before you choose a Medigap plan, it helps to think about your own health and medical needs. Ask your doctor which specialists you see regularly and how often you expect to need hospital care, urgent care, or emergency room visits. This information helps you understand which plan would cost you the least overall.

When you contact insurance companies for quotes, ask: What is the monthly premium? What is the deductible, if any? What copayments or coinsurance would I owe? Does the plan cover out-of-network providers? How do I file a claim? What is the process if I need to switch plans later?

If you are unsure which plan is right for you, your State Health Insurance information Program offers free counseling. Call 1-800-MEDICARE to reach your local SHIP office.

Frequently Asked Questions

Can I have both a Medigap plan and a Medicare Advantage plan?

No. You can have either Original Medicare with a Medigap plan, or Medicare Advantage. You cannot have both at the same time. If you have a Medigap plan and want to switch to Medicare Advantage, you would cancel the Medigap plan first.

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

Your current Medigap plan may not be available in your new state, or the premium may be different. Contact your insurance company before you move to find out whether your plan is available where you are going. You may need to switch to a different plan or insurance company. If you do switch, you have may provide issue rights if you move out of state, so the new company cannot deny you or charge you more for pre-existing conditions.

Do I need a Medigap plan if I have retiree health insurance from my former employer?

Not necessarily. If your employer coverage is as good as or better than Medigap, you may not need it. However, if your employer coverage ends, you may be able to enroll in Medigap with may provide issue rights. Ask your employer's benefits office whether you would have this protection before you turn down a Medigap plan.

What if I cannot afford a Medigap premium?

Some states offer programs to help low-income seniors pay Medigap premiums. Ask your State Health Insurance information Program whether you may be may be able to access. You can also compare plans to find a less expensive option — Plan A or Plan K cost less than Plan G or Plan N, though they cover fewer costs.

Can an insurance company drop me from my Medigap plan?

An insurance company can stop selling a particular Medigap plan in your state, but if it does, it must allow you to switch to another plan from the same company without a waiting period or health check. If the company stops selling Medigap altogether in your state, it must give you at least 30 days' notice and help you switch to another company's plan with may provide issue rights.