Every fall, Medicare beneficiaries have a critical window to review and change their coverage. The Medicare Annual Enrollment Period (AEP) runs from October 15 to December 7 each year — and missing it or ignoring it can mean paying more than necessary or staying stuck in a plan that doesn’t meet your needs.
This guide walks you through everything you need to know and do during open enrollment.
What Is the Medicare Annual Enrollment Period?
The AEP is the main opportunity each year for Medicare beneficiaries to:
- Switch from Original Medicare (Parts A & B) to a Medicare Advantage (Part C) plan
- Switch from Medicare Advantage back to Original Medicare
- Change from one Medicare Advantage plan to another
- Join, switch, or drop a Medicare Part D prescription drug plan
Changes made during AEP take effect January 1 of the following year.
Why You Should Review Every Year — Even If You’re Happy
Plans change annually. Premiums, deductibles, copays, covered drugs, and provider networks can all shift from one year to the next. A plan that was perfect last year may have:
- Dropped your doctor or specialist from the network
- Removed a medication you rely on from its formulary (drug list)
- Raised its premium or out-of-pocket maximum significantly
- Added new benefits (dental, vision, hearing, transportation) worth taking advantage of
Every September, Medicare sends an “Annual Notice of Change” (ANOC) — read it carefully before enrollment opens.
Step-by-Step: What to Do During AEP
Step 1: Gather Your Information
- List of all prescription medications (name, dosage, frequency)
- Names of your preferred doctors, specialists, hospitals
- Your current plan’s ANOC letter
- Your Medicare card
Step 2: Use Medicare’s Plan Finder Tool
Go to medicare.gov/plan-compare and enter your location and medications. The tool compares your current plan against all available plans in your area, showing total estimated annual cost — a much more useful number than just the monthly premium.
Step 3: Check Your Doctors Are In-Network
If you’re considering a Medicare Advantage plan, verify that your primary care physician, cardiologist, oncologist, or any specialist you see is in the plan’s network. Being out-of-network can mean dramatically higher costs or no coverage at all (in HMO plans).
Step 4: Check Your Medications Are Covered
Use the Plan Finder to check your specific prescriptions against each plan’s formulary. Plans use tiers — generics are cheapest, branded drugs are more expensive. Even small formulary differences can mean hundreds of dollars in annual drug costs.
Step 5: Enroll or Make Changes
You can enroll online at medicare.gov, by calling 1-800-MEDICARE (1-800-633-4227), by contacting the plan directly, or through a licensed insurance broker or SHIP counselor.
Other Enrollment Periods to Know
| Period | Dates | What You Can Do |
|---|---|---|
| Annual Enrollment Period (AEP) | Oct 15 – Dec 7 | Change any Part C or D plan |
| Medicare Advantage OEP | Jan 1 – Mar 31 | Switch MA plans or go back to Original Medicare (once) |
| Initial Enrollment Period | 7-month window around 65th birthday | First-time sign up for Medicare |
| Special Enrollment Period | Triggered by qualifying events | Changes due to moving, losing coverage, etc. |
Free Help Is Available
The State Health Insurance Assistance Program (SHIP) provides free, unbiased Medicare counseling in every state. These volunteers and staff counselors have no financial incentive to steer you toward any particular plan — they just help you understand your options. Find your local SHIP at shiphelp.org.
Frequently Asked Questions
What if I miss the Annual Enrollment Period?
If you miss AEP and don’t qualify for a Special Enrollment Period, you’ll generally be locked into your current plan until the next AEP. The Medicare Advantage Open Enrollment Period (January 1–March 31) gives MA plan members one more chance to switch.
Do I have to re-enroll every year to keep my current plan?
No. If you do nothing during AEP, you’ll remain enrolled in your current plan (if it’s still available). However, reviewing annually is still strongly recommended because the plan’s terms may have changed.
Can I switch from a Medicare Advantage plan back to Original Medicare?
Yes, during AEP (or the MA OEP January–March). However, be aware that if you switch back to Original Medicare after age 65, Medigap insurers in most states can deny you coverage or charge higher premiums based on pre-existing conditions.
What is “Extra Help” for prescription drugs?
Extra Help (also called the Low Income Subsidy) is a federal program that helps people with limited income and resources pay for Part D costs. If you qualify, you pay little or no premium and reduced copays. Apply through Social Security at ssa.gov.
Should I use an insurance broker to help choose a plan?
Brokers can be helpful — they compare multiple plans and are paid by the insurance companies, so their advice is free to you. Just understand they can only sell plans they’re contracted to sell, and may not show you every option. Using both a broker AND the medicare.gov Plan Finder gives you the most complete picture.
Your Coverage, Your Choice
Open enrollment is your power moment. It’s the one time each year when you’re fully in charge of your Medicare coverage. A few hours of review could save you hundreds of dollars and ensure your most important healthcare providers remain accessible.
Explore more Medicare guides on this site to understand your coverage options, fill the gaps, and protect your health and finances in retirement.
Recommended Reading: 10 Costly Medicare Mistakes You Can’t Afford to Make — a highly rated guide to help you make the most of your retirement.
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