You cannot change Medicare Supplement plans anytime you want. Medigap has no annual open enrollment period like Medicare Advantage does. Outside a small set of protected windows, an insurer can review your health history and either deny your application or charge you more, so timing is the difference between a guaranteed switch and getting stuck in the plan you have.
The One Window When You Can Switch Freely
Your best and easiest chance to buy or change a Medigap policy is your one-time Medigap Open Enrollment Period. It runs for six months starting the first day of the month you are both 65 and enrolled in Medicare Part B.1Medicare.gov. When Can I Buy a Medigap Policy During those six months, insurers cannot turn you down, cannot charge you more because of health problems, and cannot make you wait for coverage of pre-existing conditions.2Medicare.gov. Get Ready to Buy
The clock starts once. If you delay Part B because you still have employer coverage, the window opens when Part B begins rather than when you turn 65. Once those six months end, the federal guarantee is gone for good.
Life Events That Reopen Guaranteed Acceptance
Even after your open enrollment period closes, certain events give you “guaranteed issue rights.” When one of these applies, an insurer must sell you a policy, cover pre-existing conditions immediately, and charge you the same rate anyone else in your situation would pay.3Medicare.gov. Buying a Medigap Policy You generally have access to Plans A, B, C, D, F, G, K, or L. People who first became eligible for Medicare on or after January 1, 2020 cannot buy Plans C or F, and get Plans D and G as substitutes.1Medicare.gov. When Can I Buy a Medigap Policy
The qualifying events include:
- Your Medicare Advantage plan leaves Medicare, stops covering your area, or you move out of its service area.
- Your employer or union coverage that supplements Medicare ends, including retiree plans and COBRA.
- Your Medigap insurer goes bankrupt or your policy ends through no fault of your own.
- You leave a Medicare SELECT policy because you move out of its service area.
The deadline is strict. You have to apply no later than 63 days after the prior coverage ends, though you can apply up to 60 days before the end date if you know it’s coming.4Centers for Medicare and Medicaid Services. Choosing a Medigap Policy Miss it by a day and the guaranteed issue right is gone.
Trial Rights After Medicare Advantage
Two switching paths get their own category because they involve trying Medicare Advantage. Medicare calls these “trial rights.”
If you joined a Medicare Advantage plan when you first became eligible for Medicare at 65, you can switch to Original Medicare and buy any Medigap policy sold in your state within the first 12 months.5Medicare.gov. Learn How Medigap Works That is broader than the standard guaranteed issue set, because you can pick any plan letter.
If you dropped an existing Medigap policy to try Medicare Advantage for the first time and change your mind within 12 months, you can get your old Medigap policy back if your former insurer still sells it. If that specific policy is no longer available, you can buy Plans A, B, C, D, F, or G from any insurer in your state.4Centers for Medicare and Medicaid Services. Choosing a Medigap Policy The trial right only applies once. Go back to Medicare Advantage a second time and this protection is gone.
Where You Live Changes the Answer
Federal rules set a floor. Some states give you more.
Birthday Rule States
Roughly 15 states offer some form of “birthday rule” that opens a window around your birthday each year to switch Medigap plans without medical underwriting. The typical window is 30 to 63 days after your birthday. Most birthday rules limit you to a plan with equal or lesser benefits than your current one, so you can move from Plan G to Plan G at a cheaper insurer, but you generally cannot upgrade. Some states restrict switches to the same insurer or an affiliate. The details vary enough that you should contact your state insurance department for the exact rules.
Year-Round Switching States
Four states go further. Connecticut, Massachusetts, and New York require continuous open enrollment, so you can buy or change Medigap plans year-round with guaranteed issue protections regardless of your health. Maine requires insurers to offer at least Medigap Plan A during an annual one-month open enrollment window. In these states, stronger state protections largely override the federal restrictions described above.
If You Are Under 65
Federal law does not require insurers to sell Medigap policies to anyone under 65, even if you qualify for Medicare through a disability or end-stage renal disease.1Medicare.gov. When Can I Buy a Medigap Policy Some states require access for disabled beneficiaries; many do not. Check with your state insurance department before assuming you can switch. In many states, your first protected window arrives when you turn 65.
Trying to Switch Any Other Time
If none of the protections above cover you, switching Medigap requires passing medical underwriting. This is where most people get stuck, and it’s the reason the practical answer to “can I change anytime?” is usually no.
Underwriting means the insurer reviews your health history and decides whether to offer you a policy and at what price. There are three possible outcomes: accepted at the standard rate, accepted at a higher rate, or denied. There is no appeal if you’re denied. Conditions that commonly trigger denial include diabetes with complications, heart disease, cancer, stroke, COPD, Alzheimer’s, and use of certain medications like insulin above certain thresholds. Some applications instruct agents not to submit the paperwork at all if the applicant answers “yes” to any health question.
Applications typically ask about your health over the past two to five years, including hospitalizations, prescription medications, and whether any doctor has recommended treatment or testing you haven’t yet completed. Functional limitations, like needing a wheelchair or requiring home health services, can also lead to denial. The people who most need to switch because their premiums are climbing are often the same people who cannot pass underwriting.
Pre-Existing Condition Waiting Periods
Even if an insurer approves you outside a protected window, it can impose a waiting period of up to six months for any condition diagnosed or treated in the six months before your new policy starts. During that waiting period, the policy won’t cover services related to that condition. If you had six months of continuous creditable coverage immediately before the new policy, the insurer must waive or shorten the waiting period. Creditable coverage includes employer plans, Medicare Advantage, and other qualifying coverage without a gap of 63 days or more.
When you switch under a guaranteed issue right, no waiting period can be imposed at all. Another reason the protected windows matter.
How to Switch Without Losing Coverage
Start by identifying which window you’re in. If you have a guaranteed issue right or a state birthday rule, pin down the exact dates before doing anything else.
Compare premiums from multiple insurers for the plan letter you want. Every Medigap policy with the same letter covers the same benefits regardless of the insurer, so a Plan G from one company is identical in coverage to a Plan G from another, and price is the only real difference.6Medicare.gov. Get Medigap Basics Your State Health Insurance Assistance Program (SHIP) can help with comparisons at no cost.
Apply to the new insurer. Inside a protected enrollment window, the insurer must accept you. Outside one, your application goes through underwriting, and you should not cancel your existing policy until you have written approval and an effective date for the new one.
Once approved, you’ll get the new policy with a 30-day review period. During those 30 days, you can cancel it for a full refund if you’re not satisfied. Keep your old and new policies overlapping through that review period so you’re never uncovered. After you’ve confirmed the new policy is active, cancel the old one. Canceling too early is one of the costliest mistakes people make in this process.