Medicare is not free. As an enrollee, you're still responsible for certain costs—such as premiums, deductibles, coinsurance, and copayments. These out-of-pocket costs are sometimes called the "gaps" in Medicare coverage.

Medigap helps pay for those gaps, similar to retiree insurance.

What is Medigap and how does it work?

Sold by private companies, Medigap is a supplemental insurance policy that can be used alongside original Medicare (Parts A and B) to fill gaps in coverage. It can help you cover costs related to deductibles, copayments, coinsurance, and more.

Some Medigap policies provide coverage for medical services that don’t fall under original Medicare. One example is doctor or hospital visits that take place when you’re traveling in another country. A Medigap policy will typically pay the difference between the total healthcare costs and the Medicare-approved amount.

You must be enrolled in Medicare Part A and Part B in order to obtain a Medigap policy. A Medigap plan can be purchased from any insurance carrier that's licensed in your state to sell one. Medigap policies are standardized in most states (Plans A, B, D, G, K, L, M, and N), meaning the coverage is the same no matter which company sells it—though prices can vary.

What is Medigap vs. Medicare Advantage?

You might be wondering if a Medigap policy is the same as a Medicare Advantage (Part C) plan. The answer is no. Medicare Advantage plans are an alternative way to obtain Medicare Part A and Part B benefits once you qualify. In contrast, the purpose of a Medigap policy is to bridge the gaps in your original Medicare coverage. It’s purely a supplemental type of plan. But it's important to note that a Medigap policy cannot be used with Medicare Advantage; it can only be used with original Medicare.

What is the average monthly cost of a Medigap plan?

Medigap is an optional insurance policy. If you choose to get one, you’re responsible for paying a monthly premium from the private insurance carrier. This cost is in addition to the monthly Part B premium you pay to Medicare. Monthly Medigap premiums vary widely by plan.

What is Medigap coverage used for?

For the most part, Medigap plans are designed to cover out-of-pocket costs for services that are covered by Medicare. It's not intended to cover care that Medicare doesn’t cover that an enrollee has to pay for entirely out-of-pocket. For example, Medigap plans do not cover dental and vision costs, since original Medicare does not provide routine dental and vision coverage.

What is the downside to Medigap plans?

Medigap plans help cover out-of-pocket costs original Medicare doesn’t. But they come with some drawbacks, including: 

• High monthly premiums, in some cases
• No coverage for prescription drugs, dental, or vision care
• Cannot be used with Medicare Advantage plans

If you miss your initial enrollment window, you may face higher costs or be denied coverage altogether. Also, unlike some Medicare Advantage plans, Medigap policies do not include extra benefits (e.g., fitness memberships).

When can I buy a Medigap policy?

The ideal time to buy a Medigap policy is when you’re 65 or older and first enrolled in both Medicare Part A and Part B. This six-month window is called your Medigap Open Enrollment Period. During this time, you can buy any Medigap policy available in your state—even if you have pre-existing health conditions. In most cases, you cannot change your Medigap coverage outside your Medigap Open Enrollment Period. Use Medicare’s online tool to find out if you have a legal right to switch or drop Medigap policies.

Can I get help choosing a Medigap plan?

You can compare different Medigap policies using Medicare.gov's Medigap Policy Finder. If you have questions or need advice, consider reaching out to your State Health Insurance Assistance Program, or SHIP. SHIP counselors undergo rigorous training in Medicare matters. They are there to offer 100% unbiased, supportive guidance as you explore your options, including Medigap.