What Is Medigap Insurance? A Plain-Language Guide to Medicare Supplements

Original Medicare covers a lot, but it does not cover everything, and the pieces it leaves behind, the deductibles, the coinsurance, the 20% you owe on so many services, can add up quickly. That is the gap a Medigap policy is built to close. If you have heard the term and were not sure what it meant, here is the plain version.

So let’s answer it plainly: what is Medigap insurance, how does it work, and who is it for?

What Is Medigap Insurance?

Medigap, also called Medicare Supplement insurance, is private insurance that works alongside Original Medicare to help pay the costs it does not fully cover. Those costs include things like copayments, coinsurance, and deductibles. The name says it plainly: it fills the “gaps” in Original Medicare.

A Medigap policy does not replace Medicare. It sits on top of it. Medicare pays its share of a covered service first, and then your Medigap policy pays some or all of what is left. About 80% of people on Original Medicare carry some form of supplemental coverage, because the out-of-pocket costs on their own can be unpredictable.

How Does Medigap Work?

To buy a Medigap policy, you must be enrolled in Original Medicare, Part A and Part B. You then pay a monthly premium to a private insurance company, on top of your Part B premium, and in return the policy covers most of your remaining out-of-pocket costs for Medicare-approved services.

Two features make Medigap especially appealing to people who value predictability. First, there are no network restrictions. You can see any doctor or hospital in the country that accepts Original Medicare, without referrals. Second, your costs become far more predictable, since the policy absorbs the coinsurance and copays that would otherwise pile up.

The Standardized Plans: A Through N

Here is the part that makes Medigap easier than it looks. All Medigap policies are standardized and labeled with letters: A, B, D, G, K, L, M, and N, among others. Standardization means a Plan G from one insurer offers the exact same core benefits as a Plan G from another insurer. The coverage is identical by law. Only the premium and the company differ.

That is a genuine advantage when shopping. Once you decide which plan letter fits your needs, you simply compare price and the insurer’s reputation, not confusing benefit charts.

For most new enrollees today, the choice often comes down to a couple of plans. Plan G is the most comprehensive option available to those newly eligible, covering nearly all out-of-pocket costs so that you are generally only responsible for the Part B deductible, which is $283 in 2026. On the lower-premium end, plans like K and L share costs with you up to an annual out-of-pocket limit, $8,000 and $4,000 respectively in 2026, after which they pay 100%. (Plans C and F, which are even more comprehensive, are only available to people who became eligible for Medicare before 2020.)

What Medigap Does Not Cover

Medigap is focused on filling Original Medicare’s gaps, not adding new categories of coverage. Standard Medigap plans generally do not include prescription drugs, so you would still want a separate Part D plan. They also typically do not cover routine dental, vision, hearing, or long-term care. If those extra benefits matter most to you, that is one of the trade-offs to weigh against a Medicare Advantage plan.

Medigap vs. Medicare Advantage

This is the fork in the road for most people. You cannot have both a Medigap policy and a Medicare Advantage plan at the same time. Medigap pairs with Original Medicare and prioritizes provider freedom and predictable costs, usually at a higher monthly premium. Medicare Advantage bundles everything into one plan, often at a lower premium with extra benefits, but with network rules. Neither is universally better; it depends on what you value.

To understand the coverage all of this builds on, our guide on what Medicare is breaks down the four parts.

When to Enroll: The Window That Matters

Timing is the single most important thing to know about Medigap. Your best opportunity is the Medigap Open Enrollment Period, a one-time, six-month window that begins when you are 65 or older and enrolled in Part B. During this window, coverage is guaranteed-issue, meaning insurers cannot deny you or charge more based on your health.

After that window closes, in most states insurers can use medical underwriting, which means they can turn you down or charge more based on your health history. That is why enrolling when you are first eligible often matters so much.

Frequently Asked Questions

A few of the questions people ask most often when they are first working out what Medigap insurance is.

Is Medigap the same as Medicare Supplement insurance?

Yes. Medigap and Medicare Supplement insurance are two names for the same thing: private policies that help pay the out-of-pocket costs Original Medicare leaves behind.

Can I have Medigap and Medicare Advantage together?

No. You cannot use both at once. Medigap works only with Original Medicare. If you enroll in a Medicare Advantage plan, you cannot also use a Medigap policy.

Does Medigap cover prescription drugs?

Generally no. Standard Medigap plans do not include drug coverage, so you would typically add a separate Part D plan for prescriptions.

When is the best time to buy Medigap?

During your six-month Medigap Open Enrollment Period, which starts when you are 65 and enrolled in Part B. In that window, coverage is guaranteed-issue, so insurers cannot deny you or raise your price based on health.

Find the Plan That Fits

Understanding what Medigap insurance is helps you decide whether predictable costs and provider freedom are worth the premium for your situation. There is no reason to sort through the plan letters alone.

When you are ready, schedule a conversation with Goldway Capital. We will explain your Medicare options in plain language, at a comfortable pace, with no pressure and no obligation. You can also explore our resource center for more plain-language guides.

This information is for educational purposes only and does not constitute legal, financial, or insurance advice. Goldway Capital LLC | NPN 22184664 | Not affiliated with or endorsed by Medicare, the federal government, or any government agency. Please contact Medicare.gov or 1-800-MEDICARE for official information on all of your options.