A Medicare Supplement policy covers costs that Original Medicare leaves you to pay

A Medicare Supplement policy (also called Medigap) is insurance you buy from a private company to cover the gaps in Original Medicare. Original Medicare — Part A and Part B — does not pay for everything. You pay a deductible before Medicare kicks in, you pay coinsurance (a percentage of the cost) after that, and you pay copayments for certain services. A Medigap policy picks up some or all of those out-of-pocket costs.

The policy is separate from Medicare itself. You keep your Medicare coverage and pay your Medicare premiums. You also pay a monthly premium to the insurance company selling the Medigap policy. In return, that company pays the bills Medicare does not cover — within the limits of the plan you choose.

Medigap is different from Medicare Advantage (Part C), which is an alternative way to get Medicare coverage through a private plan. With Medigap, you use any doctor or hospital that accepts Medicare. With Medicare Advantage, you usually have a network and may need referrals.

Key Takeaways

  • A Medigap policy covers deductibles, coinsurance, and copayments that Original Medicare does not pay, reducing your out-of-pocket costs.
  • You buy Medigap from a private insurance company, not from Medicare, and you pay a separate monthly premium on top of your Medicare premiums.
  • Medigap plans are standardized by the federal government — Plan A, Plan B, Plan C, and so on — so the same plan letter covers the same benefits no matter which company sells it.
  • You can only enroll in Medigap during your initial enrollment period (usually when you turn 65) or during the open enrollment period each year; outside those windows, insurers can deny you or charge more based on your health.
  • Medigap does not cover prescription drugs, long-term care, dental, vision, or hearing — you may need separate coverage for those.

How Medigap plans are standardized and what each letter covers

The federal government sets the rules for what each Medigap plan must cover. Insurance companies cannot change the benefits or add their own. This means Plan A from one company covers exactly the same things as Plan A from another company. The only difference is the monthly premium you pay.

The plans are labeled with letters: A, B, C, D, G, K, L, M, and N. Not all letters are available in every state. Plan G is the most common choice for people new to Medicare because it covers most of the costs Original Medicare does not — deductibles, coinsurance, and copayments. Plan A is simpler and cheaper but covers fewer gaps. Plan N is also popular because it costs less than Plan G but still covers most major costs.

Each plan letter has a specific list of what it covers. For example, Plan G covers the Part B deductible, coinsurance for hospital stays, coinsurance for doctor visits, and emergency care outside the United States. Plan A does not cover the Part B deductible but covers most other gaps. You can compare the exact coverage of each plan by looking at a chart from Medicare or your state insurance office.

When you can enroll in Medigap and what happens if you miss the window

You have the strongest protection when you enroll in Medigap during your initial enrollment period. This is a six-month window that starts the month you turn 65 and are enrolled in Medicare Part B. During this window, insurance companies must sell you any Medigap plan you want at the standard rate, regardless of your health history. They cannot deny you or charge you more because you have diabetes, heart disease, or any other condition.

If you miss this window, you can still enroll during the annual open enrollment period, which runs from October 15 to December 7 each year. Coverage starts January 1. During this period, you also have may provide issue rights — companies must sell you a plan without medical underwriting.

Outside these windows, insurance companies can refuse to sell you a Medigap policy, or they can charge you a higher premium based on your health. Some states have additional protections, but they vary. If you miss the initial enrollment period and do not enroll during open enrollment, you may face delays and higher costs if you want to switch plans later.

What Medigap does not cover

Medigap covers the gaps in Original Medicare, but it does not cover everything. Prescription drugs are not included — you need a separate Part D plan for that. Long-term care (nursing home, assisted living, or home care) is not covered by Medigap or Original Medicare; you would need a separate long-term care insurance policy or to pay out of pocket.

Medigap also does not cover dental, vision, or hearing services. Some Medicare Advantage plans include these benefits, but Original Medicare and Medigap do not. If you need dental work, glasses, or hearing aids, you would pay for those separately or buy a standalone dental or vision plan.

Medigap does not cover routine physical exams, routine eye exams, or routine hearing tests. It also does not cover services that Medicare does not cover at all, such as cosmetic surgery or acupuncture (with rare exceptions).

How much Medigap costs and what affects the price

Medigap premiums vary by plan, by insurance company, by state, and by your age. Plan A is typically the cheapest; Plan G and Plan N are mid-range; and Plan F (no longer sold to new enrollees) was the most expensive. A Plan G premium might range from $100 to $300 per month depending on where you live and which company sells it, but these numbers change year to year and vary widely by location.

Insurance companies use one of three methods to set premiums: community-rated (everyone in your state pays the same), age-rated (premiums increase as you age), or issue-age-rated (your premium is based on your age when you enroll and stays at that level). Issue-age-rated plans are often cheaper when you first enroll but may increase over time.

You pay the Medigap premium directly to the insurance company, separate from your Medicare premiums. You also still pay your Part B premium to Medicare. The total of all three — Medicare Part B, Medigap premium, and Part D premium if you have it — is what you pay each month for your coverage.

How to compare Medigap plans and choose one

Start by deciding which plan letter makes sense for your budget and health needs. If you want the broadest coverage and can afford it, Plan G covers the most. If you want to keep premiums low, Plan A or Plan N may work. Medicare publishes a comparison chart showing what each plan covers; your state insurance office also has one.

Once you know which plan letter you want, get quotes from multiple insurance companies. The benefits are the same, so you are comparing price only. Call companies directly or use online quote tools. Ask about discounts — some companies offer lower rates if you pay annually instead of monthly, or if you enroll in both Medigap and Part D with them.

Check the company's customer service ratings and complaint history with your state insurance department before you enroll. A slightly cheaper premium is not worth it if the company is slow to pay claims or hard to reach. After you enroll, you can switch to a different Medigap plan or company during the annual open enrollment period without medical underwriting.

Frequently Asked Questions

Do I have to buy Medigap, or can I just use Original Medicare?

No, you do not have to buy Medigap. You can use Original Medicare alone and pay the deductibles, coinsurance, and copayments out of pocket. Many people do this, especially if they are healthy and do not expect high medical costs. The trade-off is that your costs are unpredictable and could be large if you have a serious illness or injury.

Can I switch from Medigap to Medicare Advantage?

Yes. You can switch during the annual open enrollment period (October 15 to December 7) or during the Medicare Advantage open enrollment period (January 1 to March 31). If you switch to Medicare Advantage, you drop your Medigap policy. If you later want to go back to Original Medicare and Medigap, you may face medical underwriting and higher premiums unless you are in a protected enrollment period.

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

Your Medigap policy does not automatically transfer. You will need to enroll in a new Medigap policy in your new state. You have may provide issue rights during your move, so companies must sell you a plan without medical underwriting. Contact your new state's insurance office for a list of companies and plans available there.

Does Medigap cover preventive care like colonoscopies or mammograms?

Original Medicare covers most preventive services with no copayment or coinsurance. Medigap does not need to cover these because Medicare already does. However, Medigap covers the coinsurance and copayments for services that Medicare does cover but charges you for, such as certain specialist visits or lab work.

Can I enroll in Medigap if I have a pre-existing condition?

During your initial enrollment period (the six months starting when you turn 65 and enroll in Part B), yes — companies must sell you any plan at standard rates regardless of your health. Outside that window, companies can deny you or charge more based on your health history. Some states have additional protections for people with specific conditions.