Medicare Gap Insurance Fills the Costs That Original Medicare Leaves Behind

Medicare gap insurance, also called Medigap, is a policy you buy from a private insurance company to pay for costs that Original Medicare (Parts A and B) does not cover. Original Medicare covers a large share of hospital and doctor bills, but it leaves you responsible for deductibles, copayments, and coinsurance. Gap insurance steps in to pay those out-of-pocket amounts so you are not caught with a large bill after a doctor visit or hospital stay.

You can only buy Medigap if you have Original Medicare — not if you chose a Medicare Advantage plan instead. The federal government sets what each Medigap plan must cover, so the same plan letter (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 does not.

Key Takeaways

  • Medigap pays the deductibles, copayments, and coinsurance that Original Medicare does not cover, but it does not pay for services Medicare itself does not cover.
  • There are ten standardized Medigap plans (A, B, D, G, K, L, M, N, and two others), each covering a different combination of out-of-pocket costs.
  • You can buy Medigap only during your open enrollment window — usually the six months after you turn 65 and enroll in Medicare Part B — or you may pay higher premiums later.
  • The price of the same Medigap plan varies by insurance company and by state, so comparing quotes from multiple companies can save you hundreds of dollars per year.
  • Medigap does not cover dental, vision, hearing aids, or long-term care, and it does not work with Medicare Advantage plans.

The Ten Medigap Plans and What Each One Covers

The federal government defines ten standardized Medigap plans. Each plan is labeled with a letter and covers a specific set of costs. Plan G and Plan N are the most common choices for people newly turning 65, but the right plan depends on how much out-of-pocket cost you can handle and how much you want to pay in premiums each month.

Plan G covers the Part B deductible, coinsurance for hospital stays, copayments for doctor visits and outpatient services, and blood transfusions. Plan N is similar but does not cover the Part B deductible, and it charges you a copayment for some doctor visits and emergency room trips. Plan A covers fewer costs than Plan G but has a lower premium. Plan D, K, and L use a different structure: instead of covering most costs fully, they cover a percentage of costs until you reach a yearly limit, then you pay everything above that limit yourself.

Plans B, M, and the two remaining plans (C and F, which are closed to new buyers) each cover a different combination. Because the plans are standardized, you can compare them side by side: if you are looking at Plan G from Company A and Plan G from Company B, the coverage is identical, and you are only comparing price.

When You Can Buy Medigap and Why Timing Matters

You have the strongest protection when you buy Medigap during your open enrollment period, which runs for six months starting the month you turn 65 and enroll in Medicare Part B. During this window, insurance companies cannot turn you down or charge you more because of health problems you already have — a protection called may provide issue.

If you miss this window, you can still buy Medigap later, but the rules change. After your open enrollment period ends, insurance companies can refuse to sell you a policy, or they can charge you a higher premium based on your age and health history. Some states have additional protections that extend may provide issue in certain situations (for example, if you were in a Medicare Advantage plan and it left your area), but these vary by state and are not automatic.

The cost difference can be significant. Buying during open enrollment protects you from premium increases tied to your health, so the sooner you enroll, the lower your locked-in rate is likely to be. If you delay, you may face higher premiums for the rest of your life.

How Much Medigap Costs and How to Compare Plans

Medigap premiums vary widely depending on which plan you choose, which insurance company sells it, and where you live. The same Plan G might cost $120 per month from one company and $180 from another in the same state. There is no single "average" price because it depends on so many factors, but you can get specific quotes by contacting insurance companies directly or using the Medicare Plan Finder tool on Medicare.gov.

Insurance companies use three main methods to set Medigap prices: community-rated (everyone in your area pays the same price regardless of age), age-rated (your price goes up as you get older), and issue-age-rated (your price is based on your age when you buy the policy and stays the same as you age). Age-rated plans often start cheaper but increase faster over time, while issue-age-rated plans may cost more upfront but increase more slowly.

To find the lowest price, contact at least three insurance companies and ask for quotes on the same plan. Many people save $500 to $1,000 per year by comparing before they buy. You can also call 1-800-MEDICARE to ask for a list of Medigap sellers in your state.

What Medigap Does Not Cover

Medigap covers the out-of-pocket costs that Original Medicare leaves behind, but it does not cover services that Medicare itself does not cover. Dental work, vision exams, eyeglasses, hearing aids, and routine foot care are not covered by Original Medicare, so Medigap cannot cover them either. Long-term care (nursing home or in-home care) is also not covered by any Medigap plan.

If you need dental or vision coverage, you would have to buy a separate policy for those services. Some states offer limited dental and vision programs for seniors with low income, but these are not part of Medigap. Medigap also does not work alongside Medicare Advantage plans — you can have one or the other, but not both.

Switching Between Medigap Plans and Insurance Companies

You can switch from one Medigap plan to another or from one insurance company to another at any time, but the rules about may provide issue depend on when you switch. If you switch to a different plan with the same company, you usually have the right to do so without medical underwriting. If you switch to a different company, the company can ask about your health and may refuse to cover you or charge you more.

Some states have additional protections: if you are switching to a lower-cost plan or if your current plan is being discontinued, you may have may provide issue rights even when switching companies. Check with your state insurance commissioner's office or call 1-800-MEDICARE to learn what protections explore in your state.

The best time to switch is during your open enrollment period or within 63 days of losing your current coverage (for example, if your insurance company stops selling Medigap in your area). Outside these windows, you have fewer protections.

How Medigap Works With Your Medicare Claims

When you see a doctor or go to the hospital, Original Medicare processes the claim first and pays its share. Your provider then sends the remaining bill to your Medigap insurance company, which pays the portion your plan covers. In most cases, you do not have to file a claim yourself — the two insurance companies coordinate the payment automatically.

This coordination is called crossover. Your Medigap company receives the claim information from Medicare electronically and pays within a few weeks. You should receive an explanation of benefits from both Medicare and your Medigap company showing what each one paid.

If a provider does not accept Medicare, your Medigap policy will not help you, because Medigap only covers costs that Original Medicare would have covered. Make sure any doctor or hospital you use accepts Medicare before you receive care.

Frequently Asked Questions

Can I have both Medigap and Medicare Advantage?

No. You can have Original Medicare with Medigap, or you can have Medicare Advantage, but not both. If you switch from Medicare Advantage to Original Medicare, you have a may provide issue period to buy Medigap without medical underwriting, usually 63 days from when your Medicare Advantage coverage ends.

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

Your Medigap policy remains in force when you move, but you may want to shop for a new policy because prices vary by state. Some insurance companies operate in multiple states and may offer you the same plan at a different price in your new state. You have the right to switch plans or companies during your move without medical underwriting in most cases — check with your state insurance commissioner's office for the exact rules.

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

You are not required to buy Medigap. You can use Original Medicare without it, but you will be responsible for all deductibles, copayments, and coinsurance out of your own pocket. Many people find that the monthly Medigap premium is worth it to avoid large unexpected bills, but the choice depends on your health, your income, and how much financial risk you are comfortable taking.

What is the difference between Medigap and Medicare Advantage?

Original Medicare with Medigap lets you see any doctor or hospital that accepts Medicare anywhere in the country, and Medigap covers most of your out-of-pocket costs. Medicare Advantage is an alternative to Original Medicare run by private insurance companies; it usually has lower premiums but limits you to a network of doctors and hospitals, and it may charge copayments for services. The choice depends on whether you value low premiums and network restrictions or higher out-of-pocket costs and freedom to see any provider.

Can I buy Medigap if I have a pre-existing condition?

During your open enrollment period (the six months after you turn 65 and enroll in Part B), yes — insurance companies cannot turn you down or charge you more because of health problems. After your open enrollment period ends, companies can refuse to sell you a policy or charge you higher premiums based on your health. Some states offer additional protections in specific situations, so check with your state insurance commissioner's office.