The Medicare Open Enrollment Period (OEP) ends March 31. If you're already enrolled in a Medicare Advantage plan and your plan isn't working, this is your last window of the year to make a change without waiting for AEP in October. This guide explains who qualifies, what changes you can make, and the exact steps to take before the deadline, with a focus on what California seniors need to know.
OEP at a Glance
- Dates: January 1 to March 31, 2026
- Who qualifies: people already enrolled in Medicare Advantage
- How many changes: one only during the window
- New plan effective date: first of the month following enrollment
- If you miss it: wait for AEP (Oct 15 - Dec 7) for changes
What is the Medicare Open Enrollment Period (OEP)?
The OEP is a three-month window at the start of the year when Medicare Advantage members can make a change to their coverage. It is different from the Annual Enrollment Period (AEP) in fall, which is open to everyone. OEP is exclusive to people already in a Medicare Advantage plan.
Who qualifies for the OEP?
OEP is for people already enrolled in a Medicare Advantage plan as of January 1. If you only have Original Medicare (Parts A and B), you cannot use OEP to enroll in a Medicare Advantage plan; you'd need to wait until AEP.
Why California seniors switch plans during OEP
- Their doctor is no longer in the plan's network
- Their prescriptions changed tier and now cost more
- The plan's premiums or copays are higher than expected
- They want extra benefits (dental, vision, hearing, transportation)
- They moved to a county where the plan doesn't have coverage
- They became dual-eligible (Medi-Cal + Medicare) and want a D-SNP
What changes can you make during OEP?
- Switch from one Medicare Advantage plan to another
- Drop Medicare Advantage and return to Original Medicare with a Part D plan
- Enroll in a Medigap plan if returning to Original Medicare (subject to California's guaranteed issue rules)
What you cannot do during OEP: switch from Original Medicare to a Medicare Advantage plan if you weren't in one on January 1. For that, wait until AEP.
How to switch plans before March 31: step by step
Step 1: Identify what isn't working
List what you don't like about your current plan: high costs, out-of-network doctors, uncovered medications, missing benefits. This guides you to the right alternative.
Step 2: Use the Medicare Plan Finder
Go to medicare.gov/plan-compare and compare plans available in your zip code. Filter by your medications, preferred doctors, and extra benefits.
Step 3: Verify your doctors are in the network
Before enrolling, call each doctor you see regularly and confirm they accept the new plan for 2026.
Step 4: Talk to a licensed local agent
A bilingual California agent can compare plans with you, verify networks and drug formularies, and process enrollment at no cost. Contact Medicare California to talk to an agent.
Step 5: Enroll before March 31
You can enroll online, by phone, or with your agent. Your new plan starts the first of the following month.
Not sure if you should switch?
Talk to a licensed agent free, no obligation. We help you compare your current plan with the alternatives in your zip code.
Talk to an AgentWhat happens after March 31?
After OEP, you can't switch Medicare Advantage plans until the next AEP (October 15 to December 7, 2026), unless you qualify for a Special Enrollment Period (SEP) due to a life event: moving outside the service area, losing employer coverage, qualifying for Medi-Cal or Extra Help, entering or leaving a nursing home, among others.
Are you turning 65 soon? Your situation is different
If you're turning 65 this year, your window is the Initial Enrollment Period (IEP), not OEP. The IEP is 7 months centered on your birthday month. See our complete guide to turning 65 and enrolling in Medicare in California.
Pre-March 31 checklist
- Confirm you were enrolled in Medicare Advantage as of January 1
- List what isn't working in your current plan
- Identify your essential doctors and prescriptions
- Compare at least 3 alternative plans on medicare.gov
- Verify networks with each doctor's office
- Calculate the expected total cost of the new plan, not just the premium
- Enroll before March 31