How to Change Your Parent's Medicare Plan: A Step-by-Step Guide

One of the most common questions from adult children helping with a parent's Medicare is: can we change their plan? The answer depends entirely on which plan type they're in and what time of year it is. Medicare has strict enrollment windows, and making the wrong switch at the wrong time can create coverage gaps or permanently limit future options.

This guide walks through every scenario: changing Medicare Advantage plans, switching between Medicare Advantage and Original Medicare, changing Part D drug plans, and what to do if your parent urgently needs to switch outside normal windows.

The Three Windows When Plan Changes Are Allowed

Medicare plan changes don't happen on demand. There are defined windows each year, plus special circumstances that open additional windows. Outside of these, your parent is locked into their current plan.

Annual Open Enrollment Period (OEP): October 15 – December 7

This is the main window. During OEP, beneficiaries can:

• Switch from one Medicare Advantage plan to another
• Switch from Medicare Advantage to Original Medicare (and add a standalone Part D plan)
• Switch from Original Medicare to Medicare Advantage
• Change their standalone Part D drug plan
• Add a Part D plan if they didn't have one (though late enrollment penalties may apply)

Changes made during this window take effect January 1 of the following year.

Medicare Advantage Open Enrollment Period (MA-OEP): January 1 – March 31

This is the "buyer's remorse" window specifically for Medicare Advantage enrollees. If your parent joined a Medicare Advantage plan during the fall OEP (or was auto-enrolled at 65) and it isn't working out, they can:

• Switch to a different Medicare Advantage plan
• Drop Medicare Advantage and return to Original Medicare

They cannot use this window to switch from Original Medicare into Medicare Advantage. Changes during MA-OEP take effect the first day of the following month.

Important limitation: Returning to Original Medicare during MA-OEP does not automatically give your parent Medigap Guaranteed Issue rights. In most states, they'll need to pass medical underwriting to get a Medigap plan — which means if they developed a health condition since age 65, they may be denied or charged significantly higher premiums.

Special Enrollment Periods (SEPs): Triggered by Life Events

Certain circumstances allow plan changes outside the normal windows. Common SEPs that apply to family caregiving situations:

Parent moves: If your parent relocates outside their Medicare Advantage plan's service area, they get a 2-month window to pick a new plan. This is important for adult children who move a parent to their city or into a care facility in a different region.

Plan terminates: If an insurer discontinues a plan, affected beneficiaries receive a Special Enrollment Period to choose a replacement.

5-Star Plan SEP: If a Medicare Advantage or Part D plan earns a 5-star rating from CMS, beneficiaries can switch to it once per year outside of normal OEP. Not all areas have 5-star plans, but it's worth checking.

Loss of creditable coverage: If your parent loses coverage from an employer or union plan, they have an SEP to enroll in Medicare and associated plans.

Scenario 1: Changing from One Medicare Advantage Plan to Another

This is the simplest change. During either OEP (October–December) or MA-OEP (January–March):

1. Go to medicare.gov/plan-compare or call the plan you want to switch to
2. Select the new plan and complete enrollment
3. The old plan cancels automatically — you do not need to contact the current plan to disenroll
4. Confirm the new plan card and plan information arrives before January 1 (for OEP changes)

Before switching, verify:

• Your parent's doctors are in the new plan's network
• Current medications are on the new plan's formulary at an acceptable tier
• The new plan's Maximum Out-of-Pocket (MOOP) is comparable or lower

Scenario 2: Switching from Medicare Advantage to Original Medicare

This move is sometimes made when:

• A parent needs a specialist outside their plan's network
• Prior authorization denials are creating treatment delays
• They need to access a specific hospital (e.g., a major cancer center) that doesn't accept their Advantage plan

The process: During OEP or MA-OEP, simply enroll in a standalone Part D plan. Dropping Medicare Advantage and returning to Original Medicare happens automatically once a Part D plan is selected (or you can explicitly disenroll by contacting your current MA plan).

The Medigap problem: Here is where families often get caught off guard. Original Medicare on its own has no out-of-pocket maximum — your parent is responsible for 20% of all costs indefinitely. To cap that exposure, they need a Medigap (Medicare Supplement) policy.

But in most states, if your parent is outside their initial 6-month Medigap Open Enrollment Period (which ran when they first enrolled in Part B at 65), insurers can medically underwrite them. If they've developed diabetes, heart disease, cancer, or most other chronic conditions since age 65, they may be denied a Medigap policy or quoted a prohibitively high premium.

States with extra protections: If your parent lives in California, Oregon, Idaho, Illinois, Nevada, Louisiana, Kentucky, or Maryland, the "Birthday Rule" allows them to switch Medigap plans around their birthday annually without underwriting. New York, Connecticut, Massachusetts, and Maine allow year-round switching. In these states, the Medigap access problem is much less severe.

This is why the Original Medicare vs. Medicare Advantage decision at age 65 is so consequential — and why it should not be reversed lightly without understanding the Medigap underwriting implications.

Scenario 3: Switching from Original Medicare to Medicare Advantage

This change is available during the Annual OEP only (not MA-OEP). The process is straightforward — enroll in the Medicare Advantage plan through medicare.gov or directly with the insurer.

Before making this switch, understand:

• You are giving up access to any Medigap policy you currently have (Medigap and Medicare Advantage cannot be combined)
• If you want to switch back later, you may face Medigap underwriting
• You are moving into a managed care system with networks and prior authorization requirements

If your parent is healthy and wants to reduce monthly premium costs, this switch can make financial sense. But consider it carefully given the one-way-street dynamic.

Scenario 4: Changing Only the Part D Drug Plan

This is often the most beneficial change to make annually, and it's the lowest-stakes switch. Part D plans change formularies every year, so a plan that was ideal in 2025 may be mediocre in 2026 for the same medication list.

During OEP:

1. Run the Medicare Plan Finder at medicare.gov/plan-compare with your parent's current drug list
2. Sort by Total Annual Cost (premium + drug cost-sharing combined)
3. If a better plan exists, enroll in it — the new plan takes effect January 1
4. The old Part D plan cancels automatically

There's no underwriting involved in changing Part D plans. You can switch every year without penalty, which means there's no reason not to shop this during every Annual OEP.

What You Cannot Do: The Hard Limits

A few things families sometimes assume are possible but aren't:

• You cannot add a Medigap policy while enrolled in Medicare Advantage. You must be in Original Medicare to hold a Medigap policy.
• You cannot change Medicare Advantage plans mid-year outside an SEP (even if your parent's doctor just left the network — contact the plan first, as many will make an exception to process a mid-year transition in this case).
• You cannot change from Original Medicare to Medicare Advantage during MA-OEP — that window is only for people already in Medicare Advantage.
• You cannot enroll in Medicare Advantage and keep a Medigap policy simultaneously. They're mutually exclusive products.

If Your Parent Needs to Switch Urgently

If your parent's situation is urgent — a plan denial, a doctor leaving the network, a move — call 1-800-MEDICARE (1-800-633-4227) directly and explain the situation. The representatives can help identify whether an SEP applies. Also contact your state's SHIP program (State Health Insurance Assistance Program at shiphelp.org) for free, unbiased guidance.

Document everything. If a plan change is denied and you believe an SEP applies, put the appeal in writing.

Before Any Plan Change: A Quick Checklist

• [ ] Confirmed the change window is currently open (OEP, MA-OEP, or valid SEP)
• [ ] Verified parent's doctors are in the new plan's network
• [ ] Ran current drug list through Plan Finder and confirmed formulary coverage
• [ ] Understood implications for any current Medigap coverage
• [ ] Noted effective date of new plan and confirmed no coverage gap

Changing Medicare plans is manageable once you understand which windows apply and what each switch triggers downstream. The most expensive mistake isn't switching plans — it's switching without understanding what you're giving up.

The Medicare Enrollment Guide covers all of this in depth: enrollment windows, the Original Medicare vs. Medicare Advantage trade-offs, how Medigap underwriting works and when Guaranteed Issue rights apply, and how to use the Plan Finder to compare Part D costs. It's designed specifically for adult children who need the full picture, not just individual pieces.