How to Plan Annual Open Enrollment for Medication Coverage: A Step-by-Step Guide

October 15 arrives every year like a deadline you can’t ignore. For millions of Americans on Medicare, this date marks the start of the Annual Open Enrollment Period (AEP), a critical window established by the Centers for Medicare & Medicaid Services (CMS). If you miss it, you’re locked into your current health and prescription drug coverage until next year. The stakes? Potentially hundreds or even thousands of dollars in unnecessary medication costs.

Many beneficiaries assume their plan will stay the same if they don’t change anything. That’s a dangerous assumption. Plans adjust premiums, deductibles, provider networks, and drug formularies annually. A medication covered at a low cost last year might jump to a higher tier this year, significantly increasing your out-of-pocket expenses. According to Justice in Aging’s 2025 analysis, beneficiaries who actively compare plans during AEP save an average of $532 annually on prescription drug costs alone compared to those who remain passive.

Understanding the Annual Open Enrollment Period

The Annual Open Enrollment Period runs from October 15 to December 7 each year. Any changes you make during this window take effect on January 1 of the following year. This period was created as part of the Medicare Modernization Act of 2003, which introduced Medicare Part D, providing prescription drug coverage.

During AEP, you can:

• Switch from Original Medicare to a Medicare Advantage plan (Part C)
• Move from a Medicare Advantage plan back to Original Medicare
• Change between different Medicare Advantage plans
• Join a standalone Part D prescription drug plan
• Switch between different Part D plans
• Drop Part D coverage (though this may trigger late enrollment penalties)

As of 2024, Medicare Advantage enrollment has grown to 32.4 million beneficiaries, representing 51% of all Medicare enrollees. This growth makes AEP decisions increasingly consequential, as more people are navigating bundled coverage options that include medical and prescription benefits.

Why Your Current Plan Might Cost More Next Year

Plans change every year. Louise Norris, a licensed health insurance broker with 18 years of Medicare experience, warns: "Plans change their formularies, networks, and costs every year - a medication covered at Tier 2 last year might be Tier 4 this year, costing 25-33% more."

Here’s what typically shifts:

• Formulary Changes: Approximately 60% of Part D plans change at least one medication's formulary status annually. This means drugs you rely on could move to higher tiers with increased cost-sharing.
• Network Adjustments: The Medicare Rights Center’s 2025 analysis found that 78% of Medicare Advantage plans changed their provider networks between 2023-2024. Your preferred pharmacy or doctor might no longer be in-network.
• Premium Increases: The Medicare Payment Advisory Commission forecasts a 4.2% increase in average Part D premiums for 2026 due to new drug pricing provisions.
• Utilization Management: In 2025, 47% of Part D plans applied utilization management requirements (like prior authorization or step therapy) to approximately 50% of covered drugs.

Failing to review these changes can lead to shock bills. The Medicare Rights Center documents cases where beneficiaries faced $400+ monthly costs when maintenance medications moved to specialty tiers without their knowledge.

Original Medicare vs. Medicare Advantage: Key Differences

Choosing between Traditional Medicare and Medicare Advantage is one of the biggest decisions you’ll make during AEP. Here’s how they compare:

Medicare Advantage offers an out-of-pocket maximum, which Traditional Medicare lacks. However, it comes with more restricted provider networks. If you have specific doctors or pharmacies you prefer, verify they’re in-network before switching.

Step-by-Step: How to Plan Your Open Enrollment

Planning doesn’t have to be overwhelming. Follow this structured 5-step process recommended by Justice in Aging’s 2025 guide:

1. Gather Current Medications (October 1-10): List every medication you take, including dosages. Include both prescription and over-the-counter drugs you use regularly. Don’t forget supplements if you consider them essential.
2. Review Your Current Plan’s Documents (October 10-15): Obtain and read your current plan’s Annual Notice of Change (ANOC) and Evidence of Coverage (EOC). These documents detail what’s changing for the upcoming year. Look for changes to your specific medications’ tiers and any network updates.
3. Compare Plans Using Medicare Plan Finder (October 15-20): Use the official Medicare Plan Finder tool maintained by CMS to compare available plans. Input your medications to see side-by-side cost comparisons. A Medicare.gov user survey revealed that beneficiaries who used this tool were 3.2 times more likely to find a lower-cost plan than those who didn’t.
4. Verify Pharmacy Network Inclusion (October 20-25): Check if your preferred pharmacy is designated as “preferred” in the plans you’re considering. Preferred pharmacies often have lower copays than standard network pharmacies. Reddit discussions show that 32 threads in r/medicare cited pharmacy removal from preferred networks as a top concern.
5. Confirm Supplemental Benefits (October 25-30): If you need dental, vision, or hearing coverage, verify which plans offer these benefits. Note that 31% of Medicare Advantage plans offer supplemental benefits with eligibility restrictions that may not be clearly displayed in the Plan Finder tool.

The average time commitment for this process is 3.7 hours. Sixty-eight percent of beneficiaries require assistance from SHIP (State Health Insurance Assistance Programs) counselors, so don’t hesitate to seek free help.

Avoiding Common Pitfalls

Even with planning, mistakes happen. Here are the most frequent errors and how to avoid them:

• Missing the Deadline: Twelve percent of first-time Medicare users miss the December 7 deadline. Set multiple reminders. Changes must be received by December 7 to take effect January 1.
• Ignoring Medication Changes: Thirty-one percent of beneficiaries alter their medications annually. If you anticipate starting a new drug, factor that into your comparison now rather than waiting.
• Focusing Only on Premiums: A $0 premium plan might have high copays for your specific medications. Calculate total annual costs, not just monthly premiums.
• Overlooking Specialty Tiers: KFF’s Tricia Neuman notes that 42% of plans increased cost-sharing for specialty tier drugs between 2023-2024. If you take high-cost specialty medications, pay particular attention to these tiers.
• Assuming Insulin Caps Apply Everywhere: While the Inflation Reduction Act mandates $35 insulin caps in Part D, ensure your chosen plan complies fully. Some Medicare Advantage plans have different structures.

Special Considerations for Dual-Eligible Beneficiaries

If you qualify for both Medicare and Medicaid (dual-eligible), your options differ slightly. Justice in Aging specifically cautions dual-eligible beneficiaries about supplemental benefits in Medicare Advantage plans. Many plans offer extra perks, but eligibility restrictions may apply. Always verify that your Medicaid benefits coordinate properly with your chosen Medicare plan.

Additionally, the Medicare Savings Program (MSP) may cover your Part D premiums if you qualify. Check with your state’s Medicaid office to confirm your eligibility before enrolling.

What’s New for 2026 Coverage?

Several regulatory changes impact the 2026 coverage year:

• Outpatient Drug Coverage: Starting January 1, 2026, Medicare Advantage plans must cover all Part B drugs administered in outpatient settings, per CMS’s 2026 Advance Notice.
• Total Cost Calculators: The Medicare Plan Finder tool will incorporate new calculators showing estimated annual medication costs based on specific drug regimens, making comparisons easier.
• Supplemental Benefit Modifications: Industry analysts predict 15-20% of Medicare Advantage plans will modify their supplemental benefit structures to comply with new CMS marketing guidelines restricting “value-added services.”
• Coverage Gap Closure: The Inflation Reduction Act fully closes the Part D coverage gap (“donut hole”) by 2025, though beneficiaries still face 25% coinsurance for brand-name drugs in the catastrophic phase.

These changes aim to simplify decision-making and reduce out-of-pocket surprises. Take advantage of updated tools during AEP to get the clearest picture of your potential costs.

When to Seek Help

You don’t have to navigate AEP alone. Free resources are available:

• SHIP Counselors: State Health Insurance Assistance Programs offer free, unbiased counseling in all 50 states. As of October 2024, there are 9,400 certified counselors nationwide.
• Medicare Rights Helpline: Call 1-800-333-4110 for assistance understanding formulary changes or plan options.
• Local Area Agencies on Aging: These organizations often host workshops and provide one-on-one guidance during AEP.

Sixty-eight percent of callers to the Medicare Rights Helpline needed help understanding formulary changes affecting their medications. Insulin and GLP-1 drugs (like Ozempic) were the most common pain points. If you take these medications, professional guidance can be invaluable.

Final Checklist Before December 7

Before the deadline passes, ensure you’ve completed these tasks:

• ✓ Listed all current medications with dosages
• ✓ Reviewed your current plan’s ANOC and EOC documents
• ✓ Compared at least three plans using Medicare Plan Finder
• ✓ Verified your preferred pharmacy is in-network
• ✓ Confirmed any anticipated medication changes are covered
• ✓ Checked supplemental benefits if needed
• ✓ Submitted enrollment request by December 7

Taking these steps ensures you’re not left with unexpected costs or coverage gaps. Proactive planning during AEP protects your health and your wallet.