Medicare Advantage Open Enrollment Ends March 31: One Switch Allowed, But the Medigap Trap Could Cost You $3,000 a Year
Medicare Advantage Open Enrollment Ends March 31: One Switch Allowed, But the Medigap Trap Could Cost You $3,000 a Year
You are currently enrolled in a Medicare Advantage plan. The MA Open Enrollment Period closes March 31, 2026. You have one more week to make a single coverage change — and depending on your health situation, this decision is either a straightforward tweak or one of the most consequential moves you'll make in Medicare.
Here's what you need to know before the window closes, with actual numbers so you can run the math on your own situation.
What the MA Open Enrollment Period Actually Allows
The Medicare Advantage Open Enrollment Period (MA OEP) runs January 1 through March 31 every year. Per the Medicare Rights Center's March 19, 2026 update, it allows people currently enrolled in an MA plan to make one coverage change:
- Switch from your current MA plan to a different MA plan
- Switch from your MA plan back to Original Medicare (Parts A + B)
That's it. You cannot use this window to switch from Original Medicare into MA — that's what the Annual Enrollment Period in the fall is for. And if you've already made a change during this MA OEP, you're locked in until October.
Changes made during MA OEP take effect the first day of the following month. A switch made by March 31 becomes effective April 1.
The Three Scenarios — and Which One Applies to You
Scenario 1: You're unhappy with your current MA plan
Maybe your primary care doctor left the network. Maybe your drug formulary changed and your medication jumped from Tier 2 to Tier 3. Maybe the plan's specialist copays are higher than you expected.
Your move: Switch to a different MA plan in your county. Compare network rosters, drug formularies, and out-of-pocket maximums before you click confirm.
Scenario 2: You want to go back to Original Medicare
This is where it gets complicated — and expensive to get wrong. If you had Original Medicare before enrolling in MA, you may be seriously considering going back, especially if you've been frustrated by prior authorization delays or network restrictions.
Your move: You can switch back to Original Medicare during MA OEP. But read the next section carefully before you do.
Scenario 3: You're satisfied but wondering if you're overpaying
Even if you're not switching, the MA OEP deadline is a forcing function to re-run your numbers. Plans change. Your health changes. The plan that was optimal at 65 may not be the right call at 70.
⚠️ The Irreversible Decision: Medigap Underwriting
Here's the piece most people don't know until it's too late.
If you switch from MA back to Original Medicare, you will almost certainly want a Medigap (Medicare Supplement) policy to cover your out-of-pocket exposure. Original Medicare alone has no cap on what you can owe — the Part A deductible alone is $1,676 per benefit period in 2026, and it resets with each new hospitalization.
The problem: In most states, switching from MA back to Original Medicare does NOT give you guaranteed issue rights for Medigap. Insurers can medically underwrite you. If you have diabetes, heart disease, a history of cancer, or a dozen other common conditions, you may be denied coverage entirely — or quoted a premium 50-100% higher than the standard rate.
The states with continuous Medigap open enrollment (where this isn't an issue): Connecticut, Massachusetts, Maine, and New York guarantee-issue Medigap year-round regardless of health status. Missouri and Illinois have some protections. Everyone else — check your state's rules with your State Health Insurance Assistance Program (SHIP) counselor before you make this move.
This is the decision you can't take back. Once you've been medically underwritten and denied — or once you've passed the window where guaranteed issue would have applied — there's no reset button.
The Dollar Math: MA vs. Original Medicare + Medigap Plan G + Part D
Let's run a real comparison for a 65-year-old in a mid-cost city (not California or New York, where Medigap rates are higher).
Option A: Stay in a typical $0-premium MA plan
| Cost Component | Annual Amount |
|---|---|
| Monthly premium | $0 |
| Average annual out-of-pocket (moderate health) | $1,200–$2,400 |
| Maximum out-of-pocket (MOOP) if hit | $3,500–$9,350 |
| Drug costs (depends on formulary) | $300–$1,800 |
| Estimated annual range | $1,500–$13,550 |
Option B: Original Medicare + Medigap Plan G + Standalone Part D
| Cost Component | Annual Amount |
|---|---|
| Part B premium ($185/mo) | $2,220 |
| Medigap Plan G premium (~$130–$160/mo for age 65) | $1,560–$1,920 |
| Part D plan premium (~$40–$55/mo) | $480–$660 |
| Part B deductible (Plan G doesn't cover this) | $257 |
| Remaining out-of-pocket (Plan G covers most costs) | $0–$300 |
| Estimated annual total | $4,517–$5,357 |
The crossover point: If you're relatively healthy and rarely hit your MA plan's cost-sharing, MA wins on pure premium math. But the moment you have a hospital stay, a surgery, or a serious diagnosis, the calculus flips hard. Plan G's predictability is what you're paying for — knowing your worst-case year costs roughly $5,000, not $9,350.
This is exactly the kind of 10-year projection Toravine builds for your specific situation — factoring in your plan's actual MOOP, your drug list, and your utilization history — so you're not guessing at which side of the crossover you're on.
Worked Example: The $3,000 Annual Difference
Maria, age 68, lives in suburban Ohio. She enrolled in a $0-premium MA HMO plan at 65. She has Type 2 diabetes managed with metformin and a newer GLP-1 medication.
Her current situation:
- MA plan premium: $0/month
- Specialist copays: $45/visit × 12 visits = $540
- GLP-1 on Tier 3: $95/month = $1,140/year
- One urgent care visit: $65
- Total 2025 out-of-pocket: ~$1,745
She's considering switching to Original Medicare + Plan G + Part D.
Under Plan G:
- Part B + Medigap G + Part D: ~$4,900/year all-in (premiums only)
- GLP-1 under a well-matched Part D plan: potentially $35–$50/month = $420–$600/year
- Specialist visits: $0 after Part B deductible is met
- Estimated total: ~$5,100–$5,300/year
The gap is about $3,300/year in Maria's favor staying on MA — as long as she stays reasonably healthy and her GLP-1 stays on the formulary. If her MA plan reclassifies her GLP-1 to Tier 4 next year, or if she needs surgery, that math reverses fast.
The deeper issue: Maria had guaranteed-issue rights for Medigap for six months after her 65th birthday. She didn't use them. Now, at 68, with a diabetes diagnosis on her record, switching to Plan G in Ohio requires medical underwriting. She may not qualify at standard rates.
This is why the Medigap window at 65 matters so much. Not because you need it immediately — but because closing that door is permanent in most states.
What to Actually Do Before March 31
If you're considering switching MA plans:
- Pull your plan's Evidence of Coverage and confirm your doctors are still in-network for 2026
- Run your current medications through the plan comparison tool at Medicare.gov to compare formulary tiers
- Check the 2026 MOOP — it can range from $3,500 to $9,350 depending on the plan
If you're considering going back to Original Medicare:
- Check your state's Medigap guaranteed-issue rules before you disenroll from MA
- Get a quote for Medigap Plan G (or Plan N if you want lower premiums with some cost-sharing) from at least 3 carriers — premiums for the same plan vary 30–40% by insurer for identical coverage
- Find a standalone Part D plan that covers your specific medications — don't assume the cheapest premium plan is cheapest overall
If you're staying put: Set a calendar reminder for October 15. Annual Enrollment Period is when you do the comprehensive re-comparison. But use this deadline to at least pull your Explanation of Benefits from 2025 and calculate what you actually spent.
Toravine can model the 10-year cost comparison across MA, Plan G, and Plan N using your actual drug list and estimated utilization — the kind of analysis that turns a confusing three-way decision into a clear number.
The ACA Connection Worth Watching
One tangential note from the Medicare Rights Center's March 19 analysis: CMS is proposing 2027 ACA rule changes that could limit access to affordable marketplace coverage. This matters to people under 65 who are planning their Medicare entry — and to beneficiaries who have spouses or dependents on ACA marketplace plans. Proposed changes that increase cost-sharing or reduce plan options downstream can shift how families allocate health spending, including decisions about when to maximize Medicare Advantage benefits versus leaning on marketplace coverage for non-Medicare household members.
This isn't a reason to panic or change your Medicare decisions — but it's a reason to pay attention to the full household health insurance picture when you're running costs.
Bottom Line
March 31 is the deadline. If you're in Medicare Advantage and something about your plan is genuinely not working — wrong network, wrong formulary, wrong cost structure for where your health is right now — this is your only mid-year window to fix it.
The two things that matter most:
- If you switch back to Original Medicare, understand the Medigap underwriting rules in your state first. That's the irreversible decision.
- If you stay in MA, at least verify your MOOP and your drug formulary haven't changed in ways that cost you more than they should.
Run your numbers at Toravine before the window closes — because a decision made with your actual costs is always better than one made with someone else's averages.
Sources
- Proposed Rule Could Undermine ACA Coverage — Medicare Rights Center
- The Annual Deadline to Make Certain Medicare Advantage Changes Is Fast Approaching — Medicare Rights Center
- In the Affordability Alphabet Soup of the ACA and EHBs, a Link to Higher Premiums Isn’t Clear-Cut — KFF Medicare
- What the Health? From KFF Health News: RFK Jr.’s Vaccine Schedule Changes Blocked — For Now — KFF Medicare
- Many ACA Customers Are Paying Higher Premiums. Most Blame Trump and Republicans, Poll Finds. — KFF Medicare