Medigap Basics: Open Enrollment and Guaranteed Issue Rights

Original Medicare pays a large share of covered care, but not all of it. You are left with deductibles, coinsurance and copayments, and there is no yearly cap on what you can owe. Medicare Supplement Insurance, better known as Medigap, is private insurance designed to fill some of those gaps.

The most important thing to understand about Medigap is timing. At certain moments, federal law requires insurers to sell you a policy regardless of your health. At other times, an insurer can ask health questions and turn you down or charge more. This guide explains how Medigap works, when you are protected, and how to shop, drawing on Medicare.gov and the official "Choosing a Medigap Policy" guide that CMS and the National Association of Insurance Commissioners (NAIC) published in March 2026.

This site is independent and not affiliated with Medicare, CMS, NAIC or any insurer. It offers general information, not insurance, financial or legal advice. Your state may give you more rights than described here.

What Medigap is, and what it isn't

Medigap works only with Original Medicare. According to the 2026 CMS and NAIC guide, you generally need Part A and Part B to buy a policy, you pay the insurer a monthly premium on top of your Part B premium, and each policy covers one person, so spouses buy separate policies.

The Medicare & You 2027 handbook says insurers can sell only standardized plans, named in most states by the letters A through D, F, G and K through N. All plans with the same letter offer the same basic benefits no matter which company sells them. Massachusetts, Minnesota and Wisconsin standardize their policies differently.

Some limits to know, from the same handbook and guide:

• Plans C and F are available only to people who were eligible for Medicare before January 1, 2020 (Medicare & You 2027). People new to Medicare since then may be able to buy Plan D or G, which the handbook says offer the same benefits except coverage of the Part B deductible.
• Medigap plans sold after 2005 don't include prescription drug coverage (CMS and NAIC, 2026), so most people pair Medigap with a separate Medicare drug plan.
• Medigap generally doesn't cover long-term care, vision or dental care, hearing aids, eyeglasses or private-duty nursing (Medicare & You 2027).

Medicare.gov's 2026 Medigap page says standardized policies renew automatically each year even if you have health problems, and the insurer can drop you only if you stop paying premiums, weren't truthful on your application, or the company goes out of business.

Your Medigap Open Enrollment Period

Medicare.gov's 2026 guidance describes a one-time, 6-month Medigap Open Enrollment Period that starts the first month you have Part B and are 65 or older. During it, Medicare.gov (2026) says an insurer can't refuse to sell you any Medigap policy it offers, can't use medical underwriting to deny you, and can't charge more because of pre-existing health problems.

Two details matter:

• It doesn't repeat each year, unlike fall Open Enrollment (Medicare.gov, 2026).
• It is tied to Part B. The 2026 CMS and NAIC guide says that if you delay Part B because you have coverage from your or your spouse's current job, your Medigap Open Enrollment Period won't start until you sign up for Part B. Signing up for Part B early, while still on employer coverage, starts the clock anyway.

Even in this window, the 2026 guide says an insurer may delay coverage of a pre-existing condition for up to 6 months, but not if you had at least 6 months of continuous prior creditable coverage, with no break longer than 63 days.

If you are under 65 and have Medicare because of a disability or End-Stage Renal Disease, Medicare.gov (2026) says federal law generally doesn't require insurers to sell you Medigap, though some states do. Check with your state insurance department.

Guaranteed issue rights

Outside your open enrollment window, federal law protects you in specific situations, called guaranteed issue rights or Medigap protections. In these cases, the 2026 CMS and NAIC guide says the insurer must sell you a policy, must cover your pre-existing conditions, and can't charge more because of your health. The guide's federal list includes:

• Your Medicare Advantage Plan leaves Medicare, stops giving care in your area or has a significant network change, or you move out of its service area, and you switch to Original Medicare.
• You have Original Medicare plus an employer or union plan that pays after Medicare, including retiree or COBRA coverage, and that plan is ending.
• Your Medigap insurer goes bankrupt, or your policy ends through no fault of your own.
• You leave a Medicare Advantage Plan or drop a Medigap policy because the company didn't follow the rules or misled you.

In these situations you can buy one of several specific plan letters sold in your state, and the 2026 guide says to apply no later than 63 days after your coverage ends. For some situations, the same guide says you can apply as early as 60 days before your coverage ends. Keep letters, notices and claim denials showing when coverage ended.

Trial rights if you try Medicare Advantage

The 2026 guide describes two trial rights, each lasting through your first year in a Medicare Advantage Plan:

• If you joined a Medicare Advantage Plan when you were first eligible for Medicare at 65 and switch to Original Medicare within the first year, you can buy any Medigap policy sold in your state (CMS and NAIC, 2026).
• If you dropped a Medigap policy to join a Medicare Advantage Plan for the first time and leave within a year, the 2026 guide says you can get your old policy back if the same company still sells it; if not, you can buy certain other plans.

The 2027 handbook adds that most Medigap policies don't cancel automatically when you join a Medicare Advantage Plan, so you must contact the insurer to cancel, and that you may not be able to get a policy back if you leave after the trial period.

How to shop for a policy

The 2026 CMS and NAIC guide says premiums are the only difference between policies with the same letter sold by different companies, and premiums can differ widely. A sensible process:

1. Pick the plan letter that fits your needs, comparing benefits on the Medicare.gov Medigap chart.
2. Get quotes for that same letter from several insurers licensed in your state.
3. Ask how each prices its policy. The guide describes three methods: community-rated (generally the same premium regardless of age), issue-age-rated (based on your age when you buy), and attained-age-rated (based on your current age, so it rises as you get older).
4. Ask your state insurance department about complaints against insurers you're considering, as Medicare.gov's 2026 buying steps suggest.

Medicare.gov (2026) also describes a 30-day free-look period when you replace one Medigap policy with another during your open enrollment window; don't cancel the first policy until you've decided to keep the second.

Red flags

The 2027 handbook says it is illegal for anyone to sell you a Medigap policy while you're in a Medicare Advantage Plan unless you're switching back to Original Medicare, and to report it to your state insurance department if someone tries. Be cautious of any policy not clearly labeled "Medicare Supplement Insurance," which the 2026 CMS and NAIC guide says Medigap policies must be. For personal help, contact your SHIP or your state insurance department through the NAIC's directory.

Key takeaways

• Medigap works only with Original Medicare and comes in standardized lettered plans.
• Medicare.gov (2026) describes a one-time, 6-month Medigap Open Enrollment Period that starts when you have Part B and are 65 or older.
• Guaranteed issue rights protect you when certain coverage ends; the 2026 CMS and NAIC guide says to apply within 63 days.
• Trial rights let first-year Medicare Advantage members return to Original Medicare and buy Medigap.
• Compare the same plan letter across insurers and ask how each sets its premiums.

Sources

• CMS and NAIC, Choosing a Medigap Policy (March 2026)
• Medicare.gov (CMS), Get ready to buy (Medigap)
• Medicare.gov (CMS), When can I buy a Medigap policy?
• Medicare.gov (CMS), How do I buy a Medigap policy?
• Medicare.gov (CMS), Can I change my Medigap policy?
• Medicare.gov (CMS), Learn How Medigap Works
• Centers for Medicare & Medicaid Services, Medicare & You 2027 (official handbook)
• NAIC, Insurance Departments directory