Medigap Open Enrollment: When You Have Guaranteed-Issue Rights

Information checked: 2026-09-09 · Maintenance label: Evergreen check

Medigap has one window that behaves differently from everything else in Medicare, and missing it is close to irreversible.

Medigap open enrollment is the six-month period that starts on the first day of the month in which you are 65 or older and enrolled in Part B. Inside it, insurers must sell you a policy. Outside it, in most cases, they do not have to.

This guide covers the window, the situations that create guaranteed-issue rights afterwards, and what happens if you apply without one.

Key takeaway

Your Medigap open enrollment period is six months, starting the first day of the month you are both 65 or older and enrolled in Part B. It does not repeat annually. Outside it, Medicare states there is no federal guarantee that an insurer will sell you a policy, and if one does it may cost more because of your health history.

Table of contents

• The six-month window
• Guaranteed-issue rights after the window
• What happens without a guaranteed-issue right
• Decisions worth making inside the window
• Frequently asked questions
• Summary

Related guides

• Medicare Advantage 2027: How to Compare Drug, Provider, and Out-of-Pocket Changes — The Medicare Advantage alternative to compare against
• Medicare Open Enrollment 2026: Dates, Plan Changes, and What to Review — The annual window for other Medicare changes

The six-month window

Medicare defines it precisely: “the 6-month period that starts the first day of the month you're 65 or older and signed up for Part B.”

Two features make it unlike Medicare Open Enrollment. It is personal to you rather than a fixed autumn calendar, and it happens once. There is no annual Medigap window to come back to.

This is why a decision that feels reversible — trying Medicare Advantage first and switching to Medigap later — often is not.

Check your own windowWhen can I buy a Medigap policy ›The six-month window and the situations that give you guaranteed issue rights, in Medicare's own words.

Guaranteed-issue rights after the window

Certain situations still give you the right to buy. Medicare identifies these:

• You lost your Medigap coverage through no fault of your own, for example the company went bankrupt, did not follow the rules, or misled you
• Your Medicare Advantage plan is leaving Medicare, you are moving out of its service area, or the plan did not follow the rules or misled you
• You are switching from a Medicare Advantage plan back to Original Medicare, within 60 days before or 63 days after coverage ends
• You had a Medigap policy before joining a Medicare Advantage plan and now want to switch back
• Your employer coverage is ending, which also lets you sign up for Part B without a late enrollment penalty

Notice the tight timing on the third one. Sixty days before or 63 days after is a narrow corridor, and it runs from when coverage ends rather than from when you decide.

What happens without a guaranteed-issue right

Medicare's own wording is blunt: outside your Medigap open enrollment period “there's no federal guarantee that an insurance company will sell you a Medigap policy,” and if you are able to buy one “it may cost more due to past or present health problems.”

In practice that means medical underwriting. An insurer can ask health questions, price accordingly, or decline. Some states provide additional protections beyond the federal rules, so check your own state's insurance department before concluding that a door is closed.

Decisions worth making inside the window

1. Note the exact start of your own six months, from the first day of the month you are 65 or older and enrolled in Part B.
2. Decide between Original Medicare with Medigap and Medicare Advantage while both are genuinely open to you.
3. If you choose Medigap, compare identically lettered plans on price, since the benefits within a letter are standardised.
4. Ask how the insurer prices policies over time, since the pricing method affects what you pay as you age.
5. Get free help from your State Health Insurance Assistance Program rather than only from someone selling a plan.

The comparison worth doing is not which policy is cheapest this year, but which choice you can still change later. That asymmetry is the whole point of the window.

Free one-to-one helpState Health Insurance Assistance Program ›Free, unbiased Medicare counselling in every state. Counsellors are not paid commission on plan sales.

Frequently asked questions

When exactly does my Medigap window start?

The first day of the month in which you are both 65 or older and enrolled in Part B. It runs six months from there.

Does it come round every year?

No. Unlike Medicare Open Enrollment, it happens once.

Can I switch from Medicare Advantage to Medigap later?

Sometimes, under a guaranteed-issue right such as returning to Original Medicare within 60 days before or 63 days after coverage ends. Otherwise there is no federal guarantee.

Can an insurer refuse me outside the window?

Medicare states there is no federal guarantee outside your open enrollment period, and a policy that is offered may cost more because of health history. Some states add their own protections.

Are identically lettered plans the same?

Benefits within a plan letter are standardised, so comparing prices between insurers for the same letter is a meaningful comparison.

Summary

Six months, once, starting the first day of the month you are 65 or older and enrolled in Part B. That is the window where the choice is fully yours.

Afterwards you need a guaranteed-issue right, and those come with tight deadlines tied to when other coverage ends. Check your state's rules before assuming nothing is available.