Medicare Open Enrollment Guide: What You Need to Know (2025)

Medicare has specific windows when you can enroll in or change your coverage. Missing these windows—or not using them wisely—can affect your coverage and costs for the entire year. Here's your complete guide to Medicare Open Enrollment.

The Main Enrollment Periods

Annual Enrollment Period (AEP)

October 15 - December 7

This is the main window for Medicare plan changes. During AEP, you can:

• Switch from Original Medicare to Medicare Advantage (or vice versa)
• Change from one Medicare Advantage plan to another
• Join, switch, or drop a Part D prescription drug plan
• Drop Medicare Advantage and return to Original Medicare

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

Medicare Advantage Open Enrollment Period (OEP)

January 1 - March 31

If you have Medicare Advantage, you get one additional change opportunity. During OEP, you can:

• Switch to a different Medicare Advantage plan
• Drop Medicare Advantage and return to Original Medicare (with Part D if desired)

You can only make one plan change during OEP. Changes take effect the first of the month after the plan receives your enrollment.

Important: OEP is only for current Medicare Advantage enrollees. You cannot use it to switch from Original Medicare to Medicare Advantage—that requires waiting for AEP.

Initial Enrollment Period (IEP)

7 months around your 65th birthday

Your IEP starts 3 months before your birthday month, includes your birthday month, and ends 3 months after. This is when you first enroll in Medicare—Parts A, B, and D, plus Medicare Advantage or Medigap.

Special Enrollment Periods (SEPs)

Varies by qualifying event

Certain life events trigger Special Enrollment Periods that allow Medicare changes outside normal windows:

• Losing employer coverage: 8-month SEP
• Moving out of your plan's service area: 2-month SEP
• Qualifying for Extra Help or Medicaid: Ongoing SEP
• Your plan losing a star rating: SEP to switch to a higher-rated plan
• 5-Star Plan SEP: Enroll in highly-rated plans once per year, anytime

Why Annual Enrollment Matters

Even if you're satisfied with your Medicare plan, you should review your coverage during AEP every year. Here's why:

Plans Change Annually

Medicare plans can change every year:

• Premiums may increase or decrease
• Drug formularies change—your medication might move to a higher tier or be dropped
• Provider networks change—your doctor might leave the network
• Benefits change—copays, maximum out-of-pocket, extra benefits all shift

A plan that was perfect last year might not be the best choice this year.

Your Needs Change

Your healthcare situation evolves:

• New medications added
• New health conditions diagnosed
• Different doctors or specialists
• Changed travel patterns
• Different budget considerations

A plan that fit your needs last year might not fit this year.

Better Options May Exist

New plans enter the market. Existing plans improve to compete. A better option might be available that wasn't there before.

What to Review During AEP

1. Check Your Current Plan's Changes

Your plan sends an Annual Notice of Change (ANOC) each September detailing next year's changes. Review it for:

• Premium changes
• Copay/coinsurance changes
• Drug formulary changes
• Network changes
• Benefit changes

2. Verify Your Doctors

Confirm your providers will remain in-network next year. Provider directories are updated annually—check close to enrollment time.

3. Compare Your Drug Costs

Using Medicare's Plan Finder or a Medicare advisor, compare how much you'd pay for your medications under your current plan versus alternatives.

4. Consider Your Total Costs

Don't just look at premiums. Consider:

• Monthly premium
• Drug costs for your medications
• Expected copays based on your healthcare usage
• Maximum out-of-pocket limits

The lowest premium isn't always the lowest total cost.

Common Open Enrollment Questions

Q: What happens if I don't do anything during AEP? Your current plan continues with whatever changes the insurer made for next year. You won't lose coverage, but you may miss savings or better options.

Q: Can I change my plan anytime? Generally no. Plan changes are limited to specific enrollment periods. You may qualify for Special Enrollment Periods due to certain life events.

Q: Should I change plans every year? Not necessarily—but you should review every year. If your current plan is still the best fit, keep it. But don't assume that without checking.

Q: What if I miss AEP? You'll generally need to wait until the next AEP (October 15 of the following year) unless you qualify for a Special Enrollment Period. Medicare Advantage enrollees can also use OEP (January 1 - March 31).

Get Help with Your Annual Review

Comparing Medicare plans takes time—there are dozens of options in most areas. Our free Medicare review compares all available plans based on your doctors, medications, and preferences, identifying the best option for your situation.

Schedule your free Medicare review before Annual Enrollment closes.

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This article is for educational purposes. Enrollment periods and rules may change. Consult with a licensed Medicare advisor for personalized guidance.