What You Can and Cannot Do During Medicare’s Open Enrollment Period (OEP) in 2026

The Medicare Open Enrollment Period (OEP) happens every year from January 1 through March 31, and it gives Medicare Advantage (Part C) members a valuable opportunity to make changes to their coverage. But many people confuse OEP with the fall Annual Enrollment Period (AEP), which follows different rules.

To help you make confident decisions, here’s a clear and simple breakdown of what you can and cannot do during Medicare’s OEP—so you understand your options and avoid costly mistakes.

As a licensed, independent insurance agent, I’m here to guide you through these rules and help you evaluate your needs.

✅ What You CAN Do During OEP (Jan 1 – Mar 31)

During the Open Enrollment Period, Medicare Advantage enrollees are allowed to make one change to their coverage. Here are the approved options:

1. Switch from one Medicare Advantage plan to another

If your current plan isn’t meeting your needs—whether due to network changes, benefit differences, prescription costs, or personal preferences—you can change to another Medicare Advantage plan.

Your new coverage starts the first day of the month after you make the change.

2. Switch from Medicare Advantage back to Original Medicare

If you enrolled in a Medicare Advantage plan but later realized it’s not the right fit, OEP allows you to move back to Original Medicare (Part A & B).

If you return to Original Medicare, you can also:

3. Enroll in a standalone Medicare Prescription Drug Plan (Part D)

If your Medicare Advantage plan didn’t include drug coverage—or if you simply want different prescription coverage—you may enroll in a standalone Part D plan at this time.

4. Make ONE total change during OEP

You only get one opportunity to switch during this period.
Once you make a change, you cannot switch again until the next AEP (unless you qualify for a Special Enrollment Period).

❌ What You CANNOT Do During OEP

This is where most confusion happens. Here’s what is not allowed during the Medicare Open Enrollment Period:

1. You cannot switch from Original Medicare to Medicare Advantage

This option is only available during AEP (Oct 15–Dec 7) or certain Special Enrollment Periods.

2. You cannot join a Part D plan unless you are switching out of Medicare Advantage

Part D changes are only allowed if:

• You’re leaving a Medicare Advantage plan
  OR

• You already have a Medicare Advantage plan and are changing to a different one with/without drug coverage

3. You cannot switch from one standalone Part D plan to another

If you are on Original Medicare with a Part D plan, OEP does not allow you to change drug plans. Those changes must be made during AEP.

4. You cannot enroll in Medicare for the first time

If you are new to Medicare, your enrollment options fall under:

• Initial Enrollment Period (IEP)

• Special Enrollment Period (SEP), in eligible situations

OEP is strictly for current Medicare Advantage members.

✔️ Who OEP Is Designed For

OEP is an important “safety window” for people who:

• Chose a Medicare Advantage plan during AEP but aren’t satisfied
  

• Discovered their doctors are not in-network
  

• Found that their prescriptions are not covered the way they expected
  

• Want lower out-of-pocket costs or different plan benefits
  

• Had major changes in health or budget between fall and January
  

If any of these apply to you, OEP is your chance to adjust your coverage.

🧭 How to Make the Most of OEP

Talk to a licensed, independent agent

Because I’m an independent agent, I can review plans from multiple carriers—not just one—so you get unbiased guidance based on your needs, not what a company wants to sell.

⭐ Key Takeaways

• OEP runs from January 1 – March 31 every year.
  

• You can make one Medicare Advantage plan change during this time.
  

• You can switch Medicare Advantage plans or return to Original Medicare.
  

• You cannot switch Part D plans unless switching out of Medicare Advantage.
  

• OEP is only for current Medicare Advantage members.
  

• If you’re unsure about your plan, OEP is your chance to fix issues before staying locked in for the rest of the year.