Key Takeaways

• Once you’re enrolled in a Medicare Advantage plan, switching to a Supplement (Medigap) plan later is not guaranteed. You may be subject to medical underwriting unless you qualify for a special circumstance.

• The right to buy a Medicare Supplement without health questions only exists during your initial enrollment window or a few rare situations. Waiting too long to switch may close that door permanently.

Understanding the Initial Choice You Make

When you first become eligible for Medicare, usually at age 65, you’re given a one-time opportunity to choose between two distinct paths:

• Original Medicare with a Supplement (Medigap)

• Medicare Advantage (Part C)

This choice is foundational because it affects how you receive care, what you pay out of pocket, and importantly, your ability to switch plans later. Many people believe they can change freely between these options each year, but that is not entirely true.

How Medigap Works in the First 6 Months

If you want a Medicare Supplement, your best opportunity is during your Medigap Open Enrollment Period, which lasts for six months and starts the month you are both 65 or older and enrolled in Medicare Part B. During this time:

• You can buy any Medigap plan offered in your state

• You can’t be denied based on health history

• No medical underwriting is required

After this window, insurance companies can impose medical underwriting, charge more, or deny coverage entirely based on pre-existing conditions. This rule applies in most states.

Medicare Advantage Has No Underwriting

Unlike Supplement plans, Medicare Advantage plans do not require medical underwriting. You can enroll in or switch Medicare Advantage plans during designated periods, regardless of your health status. But this flexibility doesn’t apply if you later decide to move back to a Supplement plan.

That’s where many people make a costly mistake.

Annual Enrollment Doesn’t Guarantee a Seamless Switch

Each year, October 15 to December 7, Medicare’s Annual Enrollment Period (AEP) allows you to:

• Switch from Original Medicare to a Medicare Advantage plan

• Switch from one Medicare Advantage plan to another

• Drop Medicare Advantage and return to Original Medicare

However, if you switch from Medicare Advantage back to Original Medicare, and you now want to buy a Supplement (Medigap) plan, you may not be eligible without health questions.

Unless you’re in a special guaranteed issue situation, you will be subject to underwriting. That means your application can be denied.

Guaranteed Issue Rights Are Very Limited

There are only a few guaranteed issue situations where you can switch to a Medigap plan without underwriting. These include:

• You joined a Medicare Advantage plan for the first time ever and want to switch back to Original Medicare within 12 months.

• Your Medicare Advantage plan leaves your area, or you move out of the service area.

• Your employer group health coverage (including COBRA) ends.

In these cases, you have a 63-day window from the date your other coverage ends to buy a Supplement plan.

Outside of these narrow exceptions, you’re out of luck.

Timing Is Critical to Protect Your Options

The flexibility you have during your initial enrollment quickly fades after the first year. Here’s a timeline breakdown to clarify:

• Turning 65 / Enrolling in Part B: This starts your 6-month Medigap Open Enrollment Period. You can enroll in any Supplement plan with no questions asked.

• Choosing a Medicare Advantage Plan First: If you later want to go back to Original Medicare and get a Supplement, you will likely face medical underwriting unless it’s within the first 12 months of trying Advantage.

• Beyond the First Year: You can switch from Advantage to Original Medicare during AEP, but you’ll need to qualify for a Supplement on health grounds.

That first year acts like a trial period if you chose Medicare Advantage. But after that, you could be locked out of the Supplement option.

The Misunderstanding That Costs You Choice

One of the biggest misunderstandings is assuming that Medicare’s Annual Enrollment Period is like health insurance Open Enrollment—where you can switch between any plans, no questions asked.

Medicare doesn’t work that way. The freedom to move from Medicare Advantage back to Original Medicare does not come with automatic rights to a Supplement. That’s a separate process controlled by private insurers, and it can involve underwriting.

This creates a hidden barrier that many people discover too late. If you’ve developed any new health conditions since enrolling in Advantage, you may find that no Supplement carrier will accept you.

What Medical Underwriting Can Involve

When you apply for a Medicare Supplement outside your initial enrollment period or without a guaranteed issue right, the insurer may:

• Ask detailed health questions

• Require a review of your prescriptions and diagnoses

• Use your health history to deny your application or charge higher premiums

If you’ve had chronic conditions like heart disease, diabetes, or cancer, this can be a major obstacle.

Some states have special rules that allow limited switching without underwriting at certain times, but these are the exception, not the rule. Most people in most states are subject to underwriting if they apply later.

Don’t Assume Advantage Is Reversible

It’s easy to be drawn to Medicare Advantage plans. They often advertise added benefits and lower premiums. But these plans operate within specific networks, may involve prior authorizations, and limit your freedom to seek care outside your plan’s service area.

Many beneficiaries realize after enrolling that they prefer the broader access of Original Medicare with a Supplement. But by then, switching isn’t so simple.

In 2025, the rise in Advantage plan enrollment is still continuing, but many enrollees don’t know that this initial choice can be a one-way path. You need to understand that your future flexibility may be at stake.

Make a Plan That Lasts, Not Just One That Works Today

Before enrolling in either Medicare Advantage or a Supplement plan, think about your future:

• Are you in excellent health now but have a family history of chronic illness?

• Do you want the freedom to see any provider that accepts Medicare, nationwide?

• Would future travel or relocation make a restricted network plan difficult to manage?

The plan you pick now could be the one you’re stuck with later if your health changes.

Why Getting the First Move Right Matters

Too many people make their initial Medicare choice based on short-term factors—like premium amounts or what a friend recommends. But this is a long-term decision with long-term consequences.

If you want the option to be on Original Medicare with a Supplement, the best time to secure it is when you’re first eligible. Choosing a Supplement early keeps the door open. Choosing Advantage first means that door may close later.

What You Can Do Right Now

• Review your health status and history: If you have chronic conditions, it may be safer to choose a Supplement while you still can.

• Talk to a licensed agent: Someone who understands both Medicare Advantage and Supplement rules can help you understand what you’re locking in—and what you’re giving up.

• Avoid rushed decisions during AEP: Don’t switch based on plan perks alone. Consider what switching back might involve later.

• Protect your future insurability: If you choose Advantage, know that you have just 12 months to change your mind without risk.

Choose with Future Flexibility in Mind

Choosing a Medicare plan isn’t just about today’s costs or benefits. It’s about what options you want to keep open for the future. If you select a Medicare Advantage plan now, switching back to a Supplement later may be harder than you think—if not impossible.

Make your decision with full awareness of the trade-offs. Think long-term. And if you’re unsure, speak with a licensed agent listed on this website to walk through the implications based on your specific situation.