What Is the Medicare Open Enrollment Period (OEP)? A Complete Guide

Every year, thousands of Medicare beneficiaries enroll in a plan during the Annual Enrollment Period (AEP), only to realize a few weeks later that the plan they chose doesn’t quite meet their needs. That’s exactly why the Medicare Open Enrollment Period (OEP) exists.

What Is Medicare OEP?

The Medicare Open Enrollment Period runs from January 1 through March 31 each year. It allows individuals who are already enrolled in a Medicare Advantage (Part C) plan to make a one-time change to their coverage.

OEP is designed as a safety net — not a full shopping season like AEP — giving people the chance to correct a plan choice that may not be working as expected.

What Can You Do During OEP?

During OEP, you are allowed to:

• Switch from one Medicare Advantage plan to another

• Drop your Medicare Advantage plan and return to Original Medicare

• Add a standalone Part D prescription drug plan if you return to Original Medicare

Your new coverage will take effect the first day of the month following your enrollment.

What You Cannot Do During OEP

OEP has important limitations:

• You cannot switch from Original Medicare to Medicare Advantage

• You cannot make multiple plan changes

• You cannot enroll in a Part D plan unless you return to Original Medicare

• You cannot change plans if you are not already in Medicare Advantage

Because OEP allows only one change, understanding your options before acting is critical.

Why OEP Matters

Many people choose Medicare Advantage plans based on premiums or advertised benefits, only to later discover:

• Their doctor is out of network

• Prescription costs are higher than expected

• Copays add up quickly

• Certain benefits are limited or require referrals

OEP provides a chance to reassess and make an informed adjustment — without waiting until October.