What is Medigap (Medicare Supplement)?
Medigap, also called Medicare Supplement insurance, is a private policy that helps pay some of the out-of-pocket costs Original Medicare (Parts A and B) leaves you to cover — such as deductibles, copayments, and coinsurance. It works alongside Original Medicare, not instead of it: Medicare pays its share first, and your Medigap policy helps with some of what's left.
How Medigap works
Medigap plans are standardized and labeled with letters (for example, Plan G or Plan N), so a Plan G from one company covers the same benefits as a Plan G from another — the main differences are price and the company's service. Medigap policies let you see any provider in the country that accepts Medicare, with no networks. They do not include prescription drug coverage, so people with Medigap usually add a standalone Part D plan.
What to know before you buy
The best time to buy is usually during your Medigap Open Enrollment Period — the six months that begin when you are 65 or older and enrolled in Part B — because during that window you generally cannot be turned down or charged more for health reasons. Outside that window, the rules vary by state. Medigap does not work with Medicare Advantage; you have one or the other. For your full options, contact Medicare.gov, 1-800-MEDICARE, or your State Health Insurance Assistance Program (SHIP).
The standardized plan letters
Medigap is sold as a set of standardized plans named with letters — A, B, D, G, K, L, M, and N are the ones generally available to people new to Medicare today (Plans C and F are closed to most people who became eligible after 2019). Because the benefits in each lettered plan are set by law, a Plan G is a Plan G no matter which company sells it; what changes from company to company is the premium and the service. Plan G and Plan N are the two most common choices for new enrollees, and some insurers also offer high-deductible versions of certain plans that trade a lower premium for more upfront cost-sharing.
A few states are exceptions: Massachusetts, Minnesota, and Wisconsin standardize their Medigap plans differently, so the lettered system above does not apply there. Wherever you live, comparing the same lettered plan across several companies is the most direct way to see the real price difference for identical coverage.
How Medigap is priced
Two policies with identical benefits can cost very different amounts, because insurers are allowed to set premiums using one of three methods. Community-rated policies charge everyone the same regardless of age. Issue-age policies base your premium on the age you were when you bought in, and it does not rise simply because you get older. Attained-age policies start lower but increase as you age. All three can still rise over time with general inflation and medical costs.
Knowing which method a policy uses helps you compare more than this year's premium — it tells you how the price is likely to behave over the years ahead. A licensed agent or your SHIP can explain how a given plan is rated in your state.
When Medigap tends to fit
Medigap often appeals to people who want to keep any doctor or hospital nationwide that accepts Medicare, who prefer predictable monthly costs over pay-as-you-go copays, or who travel or split the year between states. The trade-offs are a higher monthly premium than most Medicare Advantage plans and a separate Part D plan for drug coverage. Whether that trade is worth it depends on your health, budget, and how you like to receive care — there is no single right answer.
Frequently asked questions
Does Medigap cover prescriptions?
No. Medigap policies sold today do not include drug coverage. If you want help with prescription costs, you typically add a standalone Medicare Part D plan.
Can I use any doctor with Medigap?
Generally yes — Medigap works with Original Medicare, so you can see any provider in the U.S. that accepts Medicare, without networks or referrals.
Is Medigap the same as Medicare Advantage?
No. Medigap supplements Original Medicare and has no networks; Medicare Advantage is a different path that provides your Part A and B benefits through a private plan, usually with a network. You cannot have both at once.
Are all Plan G (or Plan N) policies the same?
The core benefits are. Medigap plans are standardized by letter, so any company's Plan G covers the same things as another company's Plan G. The differences are the premium, how the premium is rated, and the company's customer service.
Does Medigap cover me when I travel within the U.S.?
Yes. Because Medigap works with Original Medicare and has no networks, you can use any provider in the country that accepts Medicare. Some plans also include limited foreign-travel emergency coverage.
Related guides
This is general education, not personalized advice, and plan details change every year. For all of your options, contact Medicare.gov, 1-800-MEDICARE, or your local State Health Insurance Assistance Program (SHIP) at shiphelp.org.