Medicare Advantage Open Enrollment Period (OEP)
The Medicare Advantage Open Enrollment Period (OEP) — January 1 to March 31 — gives people already in a Medicare Advantage plan a single chance to change course early in the year. It is narrower than the fall Annual Enrollment Period, and it is easy to confuse the two.
Who can use the OEP
Only people who are already enrolled in a Medicare Advantage plan on January 1 can use the OEP. If you are on Original Medicare, this window does not apply to you — your opportunity to join Medicare Advantage is the Annual Enrollment Period or a Special Enrollment Period.
The one change it allows
During the OEP you can make a single change: switch to a different Medicare Advantage plan, or drop Medicare Advantage and return to Original Medicare (adding a Part D plan if you want drug coverage). The change takes effect the first of the month after your new plan receives the request.
The Medigap catch
If you leave Medicare Advantage for Original Medicare during the OEP and want a Medigap policy, be careful: outside your one-time Medigap open enrollment window, insurers in most states can use medical underwriting. Line up your Medigap acceptance before you drop your Advantage plan, not after.
OEP vs. AEP
The fall Annual Enrollment Period (October 15 – December 7) is open to everyone and allows multiple changes. The OEP is a spring safety valve for current Medicare Advantage members only, and only for one change.
Frequently Asked Questions
When is the Medicare Advantage Open Enrollment Period?
January 1 through March 31 each year. Your change takes effect the first of the month after the plan receives your request.
Who can use the Medicare Advantage OEP?
Only people who are already enrolled in a Medicare Advantage plan on January 1. If you have Original Medicare, this period does not apply to you.
What can I do during the OEP?
You can make one change: switch to a different Medicare Advantage plan, or drop your Medicare Advantage plan and return to Original Medicare (and add a Part D plan). You cannot use the OEP to join Medicare Advantage for the first time.
Can I buy a Medigap plan during the OEP?
You can apply, but outside your one-time Medigap open enrollment window insurers can use medical underwriting, so approval and price are not guaranteed. Confirm your Medigap options before dropping Medicare Advantage.
Talk to a Licensed Medicare Advisor
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Get My Free ReviewThis information is for educational purposes only and is not legal, tax, or insurance advice. Medicare rules, premiums, and income thresholds change annually — confirm current figures with Medicare.gov, the Social Security Administration, or a licensed advisor. HealthPlan Connect is not affiliated with or endorsed by the federal Medicare program or any government agency. Last reviewed 2026-06-15 by Lynsey Brennan, Licensed Medicare Advisor (FL #G007269).