It’s Medicare Annual Enrollment Period (AEP) season — what one of our advisors calls “Joe Namath season.” Between October 15 and December 7, seniors are flooded with commercials, mailers, and doorstep salespeople all promising free extras and can’t-miss coverage.
Here’s what most of those ads won’t tell you: the choice you make between Medicare Advantage and a Medicare Supplement (Medigap) plan doesn’t always stay a choice. Depending on when you enroll and what happens to your health afterward, changing your mind later may not be an option.
Looking for a full side-by-side comparison of Medicare Advantage and Medigap? Visit our Medicare Benefits Planning page. This article focuses specifically on the enrollment timing and rules that catch people off guard.
What Is the Medicare Annual Enrollment Period (AEP)?
The Medicare AEP runs from October 15 to December 7 every year. During this window, current Medicare beneficiaries can:
- Switch from one Medicare Advantage plan to another
- Move between Medicare Advantage and Original Medicare
- Change prescription drug (Part D) coverage
- Adjust their coverage for the upcoming plan year
AEP is different from your Initial Enrollment Period (IEP) — the seven-month window centered on your 65th birthday, when you first become eligible for Medicare Part A and Part B.
The “Gotcha Moment”: Why You Can’t Always Switch Later
Most people assume Medicare works like employer coverage or an ACA marketplace plan — if you don’t like it, you just change it next year. That assumption is the source of what we call the “gotcha moment.”
In most states (New York, Connecticut, Maine, and Massachusetts are exceptions), if you enroll in a Medicare Advantage plan and are later diagnosed with a significant condition, switching to a Medigap policy during a future AEP will require medical underwriting. An insurer can deny you coverage or charge more based on that diagnosis.
A typical conversation goes like this:
Client: “I’ve had this plan for a few years and it’s been fine. But now I’ve gotten this diagnosis, and I want to switch to a Medigap plan.”
Agent: “You’ll need to go through underwriting to qualify.”
Client: “But I was told I could change my plan every year. No one ever mentioned Medigap.”
Unfortunately, “I had no idea” doesn’t get someone approved for coverage.
Compare that to how car insurance works: you can total your car on a Tuesday and switch insurers on Wednesday, maybe with a surcharge, but you can still switch. Medicare Advantage and Medigap don’t work that way — yet many consumers assume they do.
Three Reasons This Catches People Off Guard
1. Many People Never Learn Medigap Is an Option
Some agents sell Medicare Advantage exclusively. Others enroll by phone through Medicare directly, where Medigap may never come up. If someone only sees the commercials, they’re likely to land in a Medicare Advantage plan without knowing a Medigap alternative existed.
This matters most in the first six months after turning 65 and enrolling in Part B — the one window where you can buy any Medigap plan without medical underwriting, regardless of health history. Someone with a pre-existing condition like lupus who misses this window may struggle to qualify for a Medigap plan later, since many carriers list such conditions as automatic declines.
2. Trial Rights Are Widely Misunderstood
If you enroll in a Medicare Advantage plan at 65, you typically have trial rights for the first 12 months: you can switch to a Medigap plan during that period without underwriting (rules vary by state and carrier).
Once that 12-month window closes, switching — whether through trial rights expiring or during a later AEP — generally requires medical underwriting. This is exactly when many calls come in: a new diagnosis prompts someone to want better coverage, right when they’re least likely to qualify for it.
3. Medicare Advantage Is Often “Sold,” Not “Bought”
Medicare Advantage plans are frequently marketed heavily on added perks — gym memberships, dental cleanings, over-the-counter allowances — which can overshadow how the plan actually functions if you need significant care. Before enrolling, it’s worth confirming:
- Your doctors are in-network
- Your medications are well covered
- You understand how plan rules and networks could change in future years
Nationally, close to half of new Medicare enrollees now choose Medicare Advantage. Among our own clients, roughly 90% choose Medigap — though that ratio shifts as the market evolves, which is why we revisit the comparison with clients year by year.
Real Client Experiences
“I chose a Plan G. Two months later, I found out I had lung cancer. I’m so thankful I had that plan — it covered everything.”
Compare that to:
“I had no idea I couldn’t change plans. Then I got a lung cancer diagnosis, and this plan wasn’t what I thought it was.”
In Southwest Florida especially, where AEP marketing is heavy every fall, this is the season to slow down before signing anything — not speed up because a deadline is approaching.
Frequently Asked Questions
When does the Medicare Annual Enrollment Period happen?
AEP runs from October 15 through December 7 each year. Changes made during this window take effect the following January 1.
Can I switch from Medicare Advantage to Medigap without medical underwriting?
Only in specific situations — most commonly within the first 12 months of joining a Medicare Advantage plan, using trial rights. Outside that window, approval for Medigap generally requires a health screening, and pre-existing conditions can affect eligibility or cost.
What are the most common Medicare enrollment mistakes?
- Not knowing trial rights exist when switching from Advantage to Medigap
- Enrolling without confirming your doctors or medications are covered
- Missing AEP deadlines, which can limit options or raise costs
- Assuming all Medicare plans work the same way
Why is Medicare enrollment so confusing for seniors?
Rules vary by state, carrier, and plan type, and terms like Medicare Advantage, Medigap, Part A, Part B, and Part D can blur together. Heavy AEP advertising and aggressive sales tactics add to the noise, which is why many people work with a licensed agent to sort through it.
How can I avoid the “gotcha moment”?
Learn about both Medicare Advantage and Medigap before you enroll, understand what your plan does and doesn’t cover for rehabilitation or extended care, know your trial-rights timeline, and review your coverage each year rather than assuming it hasn’t changed.
Get Help Before You Decide
Medicare’s enrollment rules are unforgiving of timing mistakes in a way most other insurance isn’t. If you’re approaching AEP season, or know someone who is, it’s worth reviewing the Medicare Advantage vs. Medigap decision with a licensed agent before — not after — a health change makes the decision for you.
For a full comparison of how Medicare Advantage and Medicare Supplement plans work, visit our Medicare Benefits Planning page, or reach out to our team to talk through your specific situation.
