✔ Backed by: Centers for Medicare & Medicaid Services (Medicare.gov) · National Council on Aging. Each fact links to its source, and the full list is at the bottom of this post.

Medicare Open Enrollment runs from October 15 to December 7, and changes you make start on January 1.[6] During this season, you will hear a lot about Medicare Advantage and drug plans. One word that often gets lost in the noise is Medigap.

This coverage has its own timing rules, and they are very different from the Open Enrollment dates. Many people do not learn this until after a key window has closed. This post explains what Medigap is, when the best time to buy is, and the questions to ask before you make a change.

What Medigap is, in plain words

Medigap is also called Medicare Supplement Insurance. It is extra insurance you buy from a private company, and it helps pay your share of costs in Original Medicare.[2]

Here is why that matters. With Original Medicare, there is no yearly limit on what you pay out of pocket unless you have extra coverage, such as Medigap.[3] For some people, a supplement policy brings peace of mind about big, unexpected bills.

A few key facts from Medicare’s own guide:[4]

• Medigap works only with Original Medicare. Companies generally can’t sell you a policy if you have a Medicare Advantage Plan.
• Each policy covers one person. If you and your spouse both want one, you each need your own policy.
• You pay a monthly premium to the insurance company, on top of your Part B premium.
• Medigap policies sold after 2005 don’t include drug coverage. For that, you would need a separate Part D plan.

These policies also generally do not cover long-term care, vision, dental, hearing aids, or private-duty nursing.[2]

Same letter, same benefits, different prices

Medigap plans are standardized and named with letters, such as Plan G. Plans with the same letter offer the same benefits no matter which company sells them.[4] As Medicare puts it, “Price is the only difference between policies with the same letter sold by different companies.”[2]

That makes shopping a little easier. Once you know which letter fits your needs, you can compare companies by price and service.

It also helps to ask how a company sets its prices, because that affects what you may pay later. Medicare describes three ways:[5]

Community-rated policies generally charge everyone the same premium, no matter their age. Issue-age-rated policies base the price on your age when you buy, and the premium does not go up just because you get older. Attained-age-rated policies base the price on your current age, so the premium goes up as you age. Medicare’s guide also notes that each company decides how it sets its prices, so ask each company how its premiums have changed over time.

The window that matters most

This is the part many people miss. Under federal law, you get a six-month Medigap Open Enrollment Period. It starts the first month you have Medicare Part B and you are 65 or older.[1]

During those six months, companies must sell you any policy they offer. They also can’t use your health history to turn you down or charge you more.[7] Medicare calls this “a one-time enrollment period.” It does not come back every year.[7]

After that window, things can change. You may pay more, and a company is allowed to deny you a policy if you don’t meet its medical underwriting rules.[1] Some states give people extra rights, so it is always worth checking your state’s rules.[1]

If you have Medicare because of a disability and are under 65, federal law generally doesn’t require companies to sell you a Medigap policy. Some states have their own rules, though.[1]

Thinking about leaving Medicare Advantage? Read this first

Here is a real-life kind of situation. Dee has had a Medicare Advantage Plan for six years. This fall, she is thinking about switching back to Original Medicare and adding a Medigap policy. That can be a reasonable choice. But her six-month window passed long ago. So a company may be able to review her health history, charge more, or say no.

So the order of steps matters. Before you drop a Medicare Advantage Plan, find out whether you can get the Medigap policy you want, and at what price.

There are some special situations, called guaranteed issue rights, where a company can’t deny you a policy.[1] Medicare’s guide describes “trial rights” for people who are new to Medicare Advantage. For example, say you joined a Medicare Advantage Plan when you were first eligible at 65, and you are still within your first year. Then you can switch back to Original Medicare and buy any Medigap policy sold in your state.[5] There is also a trial right for people who dropped a Medigap policy to try Medicare Advantage for the first time.[5]

Many guaranteed issue rights have tight timing, often no more than 63 days after your other coverage ends. Medicare suggests keeping letters, notices, and claim denials that show when your coverage ended, along with the postmarked envelopes.[5]

Questions to ask before you decide

• Am I still in my six-month Medigap Open Enrollment Period, or do I have a guaranteed issue right?
• Which plan letters are sold in my state, and what do they cost from each company?
• Is this policy community-rated, issue-age-rated, or attained-age-rated?
• Will I need a separate Part D plan for my medicines?
• If I’m leaving Medicare Advantage, will a company accept me, and at what price, before I make the switch?

Free, unbiased help is available

You do not have to sort this out alone. Every state has a State Health Insurance Assistance Program, or SHIP. According to the National Council on Aging, SHIPs offer free, unbiased, one-on-one Medicare counseling, and their counselors do not sell plans or work for insurance companies. They can help you understand Medigap, compare your options, and look at costs.[8] To find your local SHIP, visit SHIPHelp.org or call 1-877-839-2675.[8]

You can say: “I have Original Medicare and I’m trying to understand my Medigap choices. Can you help me compare plans and tell me whether I have any guaranteed issue rights?”

If you think a company did not follow the rules, Medicare suggests calling your State Insurance Department.[5]

One Tru Step: Write down your Part B start date and, if you are thinking about any change this fall, book a free SHIP counseling session before December 7.

Let’s talk

What surprised you most when you first learned how Medigap works? If you have worked with a SHIP counselor, what was the most helpful thing they told you? Share your tips in the comments.

Sources and further reading

1. Medicare.gov: When can I buy Medigap? Guaranteed issue rights
2. Medicare.gov: Your coverage options
3. Medicare.gov: Compare Original Medicare and Medicare Advantage
4. CMS: Medicare Supplement Insurance: An Overview (March 2026)
5. CMS: Choosing a Medigap Policy (March 2026)
6. Medicare.gov: Joining a plan
7. Medicare.gov: Ready to buy a Medigap policy
8. National Council on Aging: What Is a State Health Insurance Assistance Program?

Sources checked October 24, 2026. General education; individual care and coverage questions require an appropriate professional.

Related Health Hubs

• Insurance and Medicare
• Healthcare Costs and Financial Assistance
• Aging Alone

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