Medigap Open Enrollment Period: When It Starts and Your Rights
The Medicare Supplement Open Enrollment Period is a six-month window during which you may choose any Medicare Supplement (Medigap) plan.
During your Medicare Supplement Open Enrollment Period, insurance companies must issue you a Medicare Supplement (Medigap) policy without asking any health questions. Your Open Enrollment Period only occurs once, and if you miss this window, you may have trouble getting supplemental health insurance coverage down the road.
Therefore, applying for a Medicare Supplement insurance policy is best when you are first eligible to protect against hefty out-of-pocket costs and ensure coverage.
Navigating Medicare can feel overwhelming, especially when you’re trying to make sense of deadlines, rights, and which plan might protect your future best. If you’re approaching Medicare eligibility or helping a loved one through the process, understanding the Medigap Open Enrollment Period is essential – it’s a one-time opportunity to secure guaranteed coverage at the best price, no matter your health history.
In this guide, we’ll explain when Medigap Open Enrollment occurs, what protections it offers, what to expect if you miss it, and which plans seniors are choosing most often today.
The Medigap Open Enrollment Period is a six-month window when you can buy any Medicare Supplement plan sold in your state without answering health questions.
It starts the first month you're both 65 or older and enrolled in Medicare Part B.
After helping Medicare clients with Medigap enrollment for more than 15 years, I consider it the most important date in the Medigap process.
Quick Answer
When: Six months, starting the first month you're 65+ and have Part B.
What it protects: Insurers can't deny you or charge more because of your health.
How often: Under federal law, it happens once and doesn't repeat each year.
If you miss it: You can still apply, but most insurers can use medical underwriting unless you have a guaranteed issue right or a state-specific protection.
In This Article
What Is the Medigap Open Enrollment Period?
It's a federal protection that gives you six months to buy a Medicare Supplement (Medigap) policy on the same terms as a perfectly healthy applicant.
According to Medicare.gov, the window begins the first month you have Part B and are 65 or older.
During those six months, an insurance company:
- Must sell you any Medigap policy it offers in your state
- Can't deny you because of your health history
- Can't charge you more because of pre-existing conditions
Open enrollment guarantees your access, not the lowest price.
Premiums still vary by insurer, ZIP code, age and tobacco use, as our Plan G cost by state breakdown shows.
About pre-existing condition waiting periods: Medicare.gov notes that even during open enrollment, a policy can delay coverage of a pre-existing condition for up to six months if you didn't have creditable coverage before applying.
That waiting period is reduced month-for-month by prior creditable coverage, and eliminated if you had at least six months of it without a break longer than 63 days, as NCOA explains.
A waiting period isn't the same as medical underwriting.
The insurer still has to sell you the policy at its standard rate. It can only delay paying its share for that one condition.
Medicare Parts A and B still cover the condition as usual either way. See Medicare and pre-existing conditions for more.
Open Enrollment vs. Guaranteed Issue
Open enrollment is your one-time window to buy any plan an insurer sells.
Guaranteed issue rights are narrower, event-triggered protections, usually with fewer plan choices and a short deadline. They're covered below.
When Does Your Six-Month Window Begin?
Your window is tied to your Part B start date, not just when you become eligible for Medicare.
For most people those happen at the same time, but not for everyone.
Example 1: Turning 65 in June
If your Part B coverage starts June 1, your Medigap Open Enrollment Period runs from June 1 through November 30.
Part B effective June 1 → Medigap open enrollment June 1 to November 30.
Example 2: Working Past 65 and Delaying Part B
Say you turn 65 in March 2027 but keep working and stay on your employer's group health plan.
Whether you can delay Part B without a penalty depends on the coverage. It generally has to be group coverage based on current employment, yours or your spouse's.
Employer size matters too. If the employer has fewer than 20 employees, Medicare usually pays first, and delaying Part B can leave you with large gaps.
Our guide to how Medicare works with employer coverage explains who pays first. In this example, assume the coverage qualifies.
You retire at 67, and your Part B starts April 1, 2029. Your Medigap Open Enrollment Period then runs April 1 through September 30, 2029.
Part B delayed until retirement at 67 → the six-month window starts with Part B, not at 65.
Delaying Part B for a valid reason doesn't cost you your Medigap window. It moves it.
One Thing I'd Watch
The mistake I see most often here is someone enrolling in Part B at 65 "just to be safe" while still on good employer coverage.
That starts the six-month clock.
If they don't buy a Medigap policy because their employer plan is still covering them, the window can close before they retire.
Can You Apply for Medigap Before Part B Starts?
Often, yes. Many insurers accept applications months before your Part B effective date, though each sets its own rules.
Your Medigap coverage can't take effect before your Part B coverage begins. If you haven't enrolled yet, start with how to sign up for Medicare.
Applying early simply lets you lock in a policy so it starts the same day as Part B.
I generally suggest starting to compare two to three months before your Part B date, so there's no gap in coverage.
What Happens If You Miss Your Open Enrollment Period?
You can still apply for a Medigap policy at any time. The difference is that the insurer usually gets to evaluate your health first.
Outside of open enrollment, and without a guaranteed issue right or state protection, an insurance company can:
- Ask health questions and review your medical history
- Decline your application
- Approve you at a higher rate class, depending on the company
- Apply a pre-existing condition waiting period of up to six months
Plenty of healthy applicants are still approved; it just isn't guaranteed anymore.
You can read more in our guide to getting a Medicare Supplement plan outside open enrollment.
Guaranteed Issue Rights: A Separate, Narrower Protection
Federal law also gives you guaranteed issue rights in certain situations, even after your open enrollment period ends.
These rights depend on the specific event, your prior coverage and when you apply.
The examples below are general federal protections from CMS's Choosing a Medigap Policy guide (published with the NAIC and distributed by state insurance departments). Your state may provide more.
| Situation | What you can buy | When to apply |
|---|---|---|
| Your Medicare Advantage plan leaves Medicare, stops serving your area, or you move out of its service area, and you return to Original Medicare | Plan A, B, K or L, plus D and G* | As early as 60 days before coverage ends, no later than 63 days after |
| You have Original Medicare plus employer, retiree, COBRA or union coverage that pays after Medicare, and that coverage is ending | Plan A, B, K or L, plus D and G* | No later than 63 days after the latest of: coverage ending, the notice of termination, or a claim denial due to termination |
| Your Medigap insurer goes bankrupt or your policy ends through no fault of your own | Plan A, B, K or L, plus D and G* | No later than 63 days after coverage ends |
| Trial right: you joined a Medicare Advantage plan (or PACE) when first eligible for Medicare at 65 and leave within the first 12 months | Any Medigap policy sold in your state | As early as 60 days before coverage ends, no later than 63 days after |
| Trial right: you dropped a Medigap policy to join Medicare Advantage for the first time and leave within 12 months | Your former Medigap policy, if the same insurer still sells it; otherwise Plan A, B, K or L, plus D and G* | As early as 60 days before coverage ends, no later than 63 days after |
| You leave a Medicare Advantage plan or Medigap policy because the company broke the rules or misled you | Plan A, B, K or L, plus D and G* | No later than 63 days after coverage ends |
*Plans D and G apply if you became eligible for Medicare on or after January 1, 2020. If you were eligible before then, Plans C and F apply instead.
Trial rights can last an extra 12 months in certain circumstances. Simplified summary; confirm your situation with Medicare.gov or your State Health Insurance Assistance Program (SHIP).
Plan N generally isn't included in the standard federal guaranteed issue plan choices. Certain trial rights and state protections may provide additional options.
If Plan N is the plan you want long-term, your open enrollment period is the dependable time to get it.
Our guaranteed issue rights guide covers each situation in more detail.
Losing employer coverage doesn't automatically trigger these rights.
The federal right generally applies when the group plan was paying after Medicare.
If you delayed Part B while working, your open enrollment period is usually the more important protection.
Do Medigap Enrollment Rules Vary by State?
Yes. Federal law sets the minimum protections, and states can add more.
The differences generally fall into three groups:
- Broader access for everyone 65+. KFF's analysis found that Connecticut, Massachusetts and New York require year-round guaranteed issue, while Maine requires it during a limited window each year. Which plans and insurers are covered still differs by state.
- Birthday or anniversary rules. States such as California and Oregon give people who already have a Medigap policy a yearly window to switch, usually to a plan with equal or fewer benefits. These rules help with switching, not first-time enrollment.
- Newer rules. The list is still changing. New Mexico's Senate Bill 21, signed in March 2026, adds a birthday-month switching window starting January 1, 2027.
- Extra qualifying events. Many states create additional guaranteed issue situations beyond the federal list, such as changes to retiree coverage.
A few states, including Minnesota, Massachusetts and Wisconsin, also standardize Medigap plans differently than the rest of the country.
Your State Health Insurance Assistance Program (SHIP) or state insurance department can confirm what applies where you live.
If You're Under 65 and Have Medicare Due to a Disability
The federal protection doesn't apply until you turn 65. As Medicare.gov explains, people under 65 generally aren't guaranteed Medigap access under federal law, though some states provide it.
KFF's analysis shows that many states require insurers to offer at least one Medigap policy to people under 65, while others don't require it at all.
Even in states that require access, the rules can limit which plans are available, and premiums can be higher than at 65.
When you turn 65, you get the standard six-month Medigap Open Enrollment Period, according to KFF.
Can You Switch Medigap Plans Later?
Yes, switching is often possible.
Outside of open enrollment, a guaranteed issue right or a state protection, the new insurer can usually require medical underwriting.
Medicare.gov notes that if you buy a policy during open enrollment and change your mind, you can switch to a different Medigap policy while the window is still open.
Here's a common example.
Someone picks Plan K at 65 because the premium fits their budget.
A few years later, they're managing a chronic condition and want Plan G.
If they're healthy enough to pass underwriting, the switch may be straightforward.
If their health has changed, they may be declined or offered a higher rate.
A Pattern I've Noticed
Clients who switch successfully usually do it while they're still healthy, often because of a rate increase rather than a health change.
The people who struggle are the ones who wait until after a diagnosis to look for more coverage.
That's why I encourage people to choose the coverage level they'd want at 75 or 80, not just the one that fits best at 65.
Is Medigap Open Enrollment the Same as Medicare Open Enrollment?
No. These are two different enrollment periods, and confusing them can affect your ability to buy a Medigap policy.
- Medigap Open Enrollment: Your six-month window begins when you're 65 or older and enrolled in Part B. Insurers can't deny you or charge more because of your health.
- Medicare Open Enrollment: Runs every year from October 15 through December 7. You can make changes to Medicare Advantage and Part D drug plans.
The fall enrollment period doesn't give you a new right to buy Medigap without medical underwriting.
Unless you qualify for guaranteed issue rights or a state protection, an insurer may review your health history before approving coverage.
If you're already in a Medicare Advantage plan, see switching from Medicare Advantage to Medigap.
How to Prepare for Medigap Open Enrollment
- Confirm your Part B start date. That date sets your window. Check your Medicare card or your Medicare enrollment confirmation.
- Decide whether you're delaying Part B. See Example 2 if you're still working.
- Think about how you use healthcare. Frequent specialist visits, ongoing conditions and travel plans all affect which plan fits.
- Choose a plan letter. Most people compare Plan G, Plan N and High Deductible Plan G. Our side-by-side comparison of all three shows how they differ.
- Compare the same plan across companies. Benefits are standardized, but premiums and pricing methods aren't. Here's how to research Medigap companies and which shopping mistakes to avoid.
- Plan for drug coverage separately. Medigap doesn't cover prescriptions. Consider enrolling in a separate Part D plan unless you have other creditable drug coverage. Going without creditable coverage can result in a late enrollment penalty.
- Apply before the window closes. Many insurers accept applications ahead of your Part B date.
Frequently Asked Questions
Does the Medigap Open Enrollment Period happen every year?
No. Under federal law, it's a one-time, six-month window.
Some states add yearly or year-round opportunities, so check your state's rules.
If I'm still working at 65, should I sign up for Part B to start my window?
Not necessarily. If your employer coverage is primary and you don't plan to buy Medigap yet, starting Part B can use up your window early.
Many people delay Part B until their employer coverage ends, then use their open enrollment period at that point.
Can I be denied Medigap during open enrollment because of a pre-existing condition?
No. The insurer must sell you any policy it offers and can't charge more because of your health.
A waiting period of up to six months may apply if you didn't have prior creditable coverage.
Can I buy Plan N with a guaranteed issue right?
Usually not.
Most federal guaranteed issue situations are limited to Plans A, B, K and L, plus D and G (or C and F if you were eligible for Medicare before 2020).
The exception is the trial right for people who joined Medicare Advantage at 65 and leave within a year. Some state rules are broader too.
Bottom Line
Here's how I'd approach your Medigap Open Enrollment Period:
- Turning 65 with no employer coverage: Start comparing two to three months before Part B begins, and apply so coverage starts with Part B.
- Still working with employer coverage: Confirm whether you can safely delay Part B without penalties or coverage gaps before deciding when to enroll.
- Already past your window: Check for guaranteed issue rights and your state's rules first. If you're in good health, applying with underwriting is still worth a try.
