What Is Medigap (Medicare Supplement) Insurance?

Original Medicare covers about 80% of medical costs. Medigap covers much of the rest. Here's a plain-English explanation of what it is and how it works.

In this guide (5 steps):

1.Understand When You Can Enroll Without Medical Underwriting
2.Compare Plans by Letter
3.Find and Compare Prices
4.Apply Through an Insurance Company
5.Understand What Medigap Does Not Cover

Understand When You Can Enroll Without Medical Underwriting

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The best time to enroll is your Medigap Open Enrollment Period: the 6 months starting on the first day of the month you are 65 AND enrolled in Part B. During this window, any insurance company must accept you at standard rates regardless of health history.

Warning

After this window closes, you may be denied coverage or charged higher premiums based on medical history. Enrolling during the open enrollment period is strongly recommended.

Compare Plans by Letter

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All Medigap plan letters (A, B, D, G, K, L, M, N) have standardized benefits across every insurance company. Plan G is popular because it covers nearly all out-of-pocket costs except the Part B annual deductible (about $240 in 2026). Compare prices for the same plan letter from different companies at your zip code.

Find and Compare Prices

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Use the official tool at medicare.gov → "Compare health plans" → "Medigap" to see available plans and approximate prices in your zip code. You can also call your State Health Insurance Assistance Program (SHIP) — a free, federally funded counseling service — at 1-877-839-2675.

Quick Tip

SHIP counselors give free, unbiased advice about Medicare plan options in your state. This is one of the most underused resources available to Medicare beneficiaries.

Apply Through an Insurance Company

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Once you have chosen a plan letter and an insurance company with a competitive price, apply directly through that company (by phone, website, or with an insurance agent). The insurance company processes your application and issues a policy. You pay the company directly each month.

Understand What Medigap Does Not Cover

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Medigap plans do not include prescription drug coverage — you need a separate Part D plan for medications. They also do not cover dental, vision, or hearing. For these services, you would need additional coverage through a standalone dental/vision plan or a Medicare Advantage plan.

Quick Tip

If you have Medigap, do NOT also enroll in a Medicare Advantage plan — they cannot be used together. Medigap works with Original Medicare only.

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Original Medicare (Parts A and B) covers most hospital and medical costs, but it does not cover everything. You are responsible for deductibles, copayments, and coinsurance — costs that can add up to thousands of dollars during a serious illness or surgery. Medigap (also called Medicare Supplement Insurance) is private insurance that covers many of these out-of-pocket costs that Original Medicare leaves unpaid.

Medigap is sold by private insurance companies but is highly regulated by the federal government. Plans are standardized and labeled with letters (Plan A, Plan B, Plan C, Plan D, Plan F, Plan G, Plan K, Plan L, Plan M, Plan N). All companies selling Plan G must offer the exact same Plan G benefits — you are only shopping for the best price, not for different coverage.

Medigap is separate from Medicare Advantage. Medigap works alongside Original Medicare — you keep your Medicare card and use any doctor or hospital in the US that accepts Medicare. Medicare Advantage plans replace Original Medicare and typically limit you to a network of providers. These are fundamentally different approaches.

Plan G

is currently the most popular Medigap plan for new Medicare enrollees (since Plan F was discontinued for those who became eligible after 2020). Plan G covers: Part A deductible and coinsurance, Part B coinsurance (the 20% Medicare does not pay), skilled nursing facility coinsurance, and foreign travel emergencies. You only pay the Part B annual deductible yourself.

The best time to enroll in Medigap is during the six-month open enrollment period that starts the month you are both 65 years old AND enrolled in Medicare Part B. During this period, insurance companies cannot deny you coverage or charge higher premiums due to pre-existing conditions.

Medigap does not cover prescription drugs (Part D), dental, vision, or hearing — these require separate coverage.

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