7 Critical Medicare Enrollment Mistakes to Avoid in 2026

Last Updated: January 27, 2026

Are you leaving thousands of dollars on the table simply by ignoring your Medicare plan during Annual Enrollment Period? With the 2026 AEP now closed as of December 7, 2025, many Lawrence, KS beneficiaries are discovering costly surprises in their January coverage. From unexpected prescription costs to doctors no longer in-network, the mistakes made during enrollment season are showing up in mailboxes and at pharmacy counters across Douglas County.

Understanding Medicare open enrollment mistakes to avoid in 2026 isn’t just about saving money—it’s about protecting your health coverage when you need it most. Whether you’re navigating Medicare Advantage changes, Part D formulary updates, or plan non-renewals, the decisions made (or not made) during last fall’s enrollment period are impacting your coverage right now. The good news? If you made a mistake, options still exist through the Medicare Advantage Open Enrollment Period running until March 31, 2026.

Quick Answer: What Are the Biggest Medicare Enrollment Mistakes?

The most costly Medicare enrollment mistakes include ignoring annual plan changes, failing to review prescription drug formularies, not verifying provider networks, waiting until the December 7 deadline, and assuming your spouse needs the same coverage. These oversights can result in thousands of dollars in unexpected out-of-pocket costs or gaps in coverage that persist throughout 2026.

Key Takeaways:

• Doing nothing during AEP is the highest-cost mistake—plan changes occur annually
• Part D formularies change yearly; medications may move to higher cost tiers or become uncovered
• Provider networks contract regularly; verify your doctors remain in-network
• The Medicare Advantage OEP (January 1–March 31) allows one plan change if you made an enrollment mistake
• Late Part D enrollment triggers a permanent 1% monthly penalty for each month without coverage

Understanding Medicare Enrollment Periods in 2026

Medicare’s Annual Enrollment Period ran from October 15 through December 7, 2025, allowing beneficiaries to make changes effective January 1, 2026. This seven-week window is when over 30 million Medicare Advantage and Part D enrollees can switch plans, add coverage, or return to Original Medicare. We work with Lawrence residents throughout the various Medicare enrollment periods and see firsthand how missing deadlines or rushing decisions creates problems that last all year.

The 2026 enrollment cycle saw significant changes across Kansas Medicare offerings. Some Medicare Advantage plans non-renewed coverage areas entirely, forcing affected beneficiaries to select new plans or automatically default to Original Medicare. In our experience serving Douglas County communities including zip codes 66044, 66046, and 66047, beneficiaries who waited until late November or early December faced limited options and rushed decisions.

Why Annual Enrollment Changes Matter

Private Medicare insurers adjust their offerings every year based on regulatory requirements and market dynamics. Premiums, copayments, deductibles, formularies (covered drug lists), and provider networks all shift annually. The Annual Notice of Change (ANOC) mailed to beneficiaries each September details these modifications, but approximately 75% of Medicare beneficiaries choose to “do nothing” and stick with their current plan—often missing opportunities for better coverage or lower costs.

According to Medicare.gov, plan changes for 2026 included adjustments to supplemental benefits, modifications to pharmacy networks, and updates to prior authorization requirements. When our team reviews plans with clients near the KU campus or in West Lawrence, we regularly find instances where last year’s optimal plan no longer offers the best value or coverage for their current health needs.

Mistake #1: Ignoring Your Annual Notice of Change

The most common and expensive Medicare enrollment mistake is simply ignoring the Annual Notice of Change document that arrives each fall. This legally required notice details every modification to your plan for the coming year—premium increases, copayment changes, formulary updates, and network adjustments. When beneficiaries discard this envelope thinking “my plan is fine,” they set themselves up for unpleasant January surprises.

A typical scenario we see: A Lawrence resident receives their ANOC in September but doesn’t open it. Come January, they discover their preferred cardiologist at Lawrence Memorial Hospital dropped out of their plan’s network, or their diabetes medication jumped from a $10 copay to $75 because it moved from Tier 2 to Tier 4 on the formulary. These changes were all disclosed in the ANOC, but without reading it, there was no opportunity to shop for better alternatives during AEP.

How to Properly Review Your ANOC

When the ANOC arrives (typically late September), open it immediately and review these critical sections:

• Premium changes: Note any increases to monthly costs
• Medical benefits: Check copays for doctor visits, specialists, hospital stays, and emergency care
• Prescription coverage: Verify your medications remain covered at the same tier
• Provider network: Confirm your doctors and preferred facilities remain in-network
• Supplemental benefits: Review changes to dental, vision, hearing, or fitness benefits

Cross-reference your current prescription list against the updated formulary. If any medications moved to higher tiers or require new prior authorizations, that’s your signal to compare alternative plans that might offer better coverage for your specific drugs.

Mistake #2: Failing to Review Prescription Drug Coverage

Part D formularies change every year, and the medication that cost $15 in 2025 might cost $150 in 2026 if it moved to a non-preferred tier or dropped from coverage entirely. This represents one of the most financially impactful Medicare open enrollment mistakes to avoid in 2026. We regularly help Lawrence residents discover their medications changed status, and when caught during AEP, we can find plans that cover those drugs at lower costs.

The Part D late enrollment penalty adds another layer of urgency. For every month you go without creditable prescription drug coverage after becoming eligible, Medicare adds a permanent 1% penalty to your monthly premium. This compounds over time—a five-month gap means approximately 5% higher premiums for life. According to the Centers for Medicare & Medicaid Services, these penalties persist as long as you have Part D coverage.

Using Medicare’s Plan Finder Tool

Medicare’s online Plan Finder at Medicare.gov allows you to enter your specific medications and dosages, then compare which plans offer the best coverage in your area. For Lawrence residents (zip codes 66044, 66046, 66047, 66049), this tool filters dozens of available plans to show total estimated annual costs including premiums, deductibles, and copays for your exact prescription regimen.

When using Plan Finder, include all your prescriptions—not just the expensive ones. Generic medications sometimes vary significantly in cost between plans, and those small differences add up over a year. Also verify pharmacy networks; if your preferred pharmacy (perhaps near 23rd and Louisiana Street or along Clinton Parkway) isn’t in-network, you’ll face higher costs or need to switch locations.

Mistake #3: Not Verifying Provider Networks

Medicare Advantage plans operate through HMO and PPO networks, and these networks contract and expand annually. A doctor who accepted your plan in 2025 may have dropped out for 2026. For HMO plans especially, seeing an out-of-network provider means paying full costs out-of-pocket except in emergencies. This common oversight among Medicare enrollment mistakes costs beneficiaries thousands when they discover their longtime physician no longer participates.

Kansas insurance regulations allow insurers to modify provider networks with proper notice, but beneficiaries must take action during AEP to respond. We’ve worked with clients whose specialists at LMH Health or clinics along Wakarusa Drive unexpectedly left their plan’s network. When caught during the October-December enrollment window, switching to a plan that includes those providers is straightforward. Discovering it in January leaves you stuck until the next AEP—or paying cash rates for care.

How to Confirm Network Status

Don’t rely solely on last year’s provider directory. Networks change, and outdated information leads to expensive mistakes. Take these steps:

• Check the plan’s current online provider directory (update for 2026 effective dates)
• Call your doctor’s office directly and confirm they accept your specific plan for 2026
• Verify not just primary care but specialists, hospitals, and ancillary providers
• For PPO plans, distinguish between in-network and out-of-network cost differences

In our experience helping Douglas County residents compare Medicare Advantage plans in Lawrence for 2026, network verification consistently uncovers discrepancies. Provider directories lag behind real-time contract changes, so confirming directly with medical offices provides the most reliable information.

Mistake #4: Waiting Until the December 7 Deadline

Procrastination during AEP creates rushed decisions and limited options. Enrollment volumes spike dramatically in late November and early December, overwhelming both insurance company systems and licensed advisors. When plans non-renew coverage areas—as happened for some Kansas regions in 2026—last-minute shoppers face fewer available alternatives and less time to properly compare options.

We recommend beginning your Medicare plan review in mid-October, shortly after ANOCs arrive. This provides six weeks to compare plans, verify networks and formularies, and make informed decisions without pressure. Starting early also allows time to resolve complications like plan non-renewals or discovering your preferred coverage is no longer available, necessitating deeper research into alternatives.

Creating an Enrollment Calendar

Mark these dates annually to avoid last-minute stress:

Date	Action
Late September	Watch for ANOC arrival; open and review immediately
October 15	AEP begins; start comparing plans if changes affect you
Late October	Complete provider network verification and formulary checks
Early November	Make enrollment decision; submit application
December 7	AEP ends at 11:59 PM local time

Set calendar reminders or work with a licensed Medicare advisor who can notify you when enrollment season approaches. Many Lawrence residents schedule annual plan reviews each October, treating it as routine maintenance like tax filing or vehicle registration.

Mistake #5: Assuming Spousal Plans Should Match

Married couples often assume they should enroll in identical Medicare plans for simplicity. This represents a subtle but expensive mistake. Each person’s health needs, prescription requirements, and preferred providers differ—sometimes dramatically. The optimal plan for one spouse may be entirely wrong for the other, leading to unnecessary costs or coverage gaps.

Consider a common scenario: One spouse takes multiple brand-name medications requiring robust Part D coverage, while the other takes only generics. The first spouse benefits from a plan with lower drug copays despite higher premiums, while the second spouse saves money with a lower-premium plan adequate for basic prescriptions. Enrolling both in the same plan means one person overpays or receives insufficient coverage.

Individualizing Medicare Coverage

Evaluate each person’s Medicare needs separately during AEP. Create individual lists of prescriptions, preferred doctors, anticipated medical needs, and budget constraints. Run each through Medicare’s Plan Finder independently. You may discover one spouse should enroll in a Medicare Advantage plan while the other prefers Original Medicare with a Medigap policy—perfectly acceptable and often more cost-effective than forcing both into identical coverage.

Mistake #6: Focusing Only on Monthly Premiums

Selecting a Medicare plan based solely on the lowest monthly premium represents penny-wise, pound-foolish thinking. Total annual costs include premiums plus deductibles, copayments, coinsurance, and out-of-pocket maximums. A $0 premium Medicare Advantage plan might seem attractive, but if it charges $60 copays per specialist visit and you see specialists monthly, annual costs exceed a plan with a $40 premium but $20 specialist copays.

For 2026, Part D premiums showed significant variation across Kansas plans due to reduced federal stabilization funding. Some plans increased premiums while others decreased, creating a complex landscape requiring holistic cost analysis. When we help clients through Medicare planning in Lawrence, KS, we calculate projected total annual costs based on their specific anticipated usage—not just the advertised premium.

Calculating True Total Cost

To compare plans accurately, estimate your total annual cost including:

• Monthly premiums × 12 months
• Annual deductibles (medical and/or drug)
• Copays for regular services (primary care, specialists, labs, imaging)
• Prescription costs based on your actual medications and dosages
• Potential out-of-pocket maximum if you have significant health needs

Medicare’s Plan Finder tool provides estimated annual drug costs, but manually calculating medical service costs requires reviewing each plan’s Summary of Benefits. The lowest-premium plan frequently delivers the highest total annual cost when actual utilization is factored in.

What to Do If You Made an Enrollment Mistake

If you’re reading this in January 2026 realizing you made a Medicare enrollment mistake, relief exists through the Medicare Advantage Open Enrollment Period (OEP) running January 1 through March 31. This window allows one plan change for beneficiaries currently in Medicare Advantage. You can switch to a different Medicare Advantage plan or drop back to Original Medicare and add Part D coverage.

OEP provides a safety net for common enrollment mistakes. Discovering your medications aren’t covered, your doctor isn’t in-network, or your chosen plan doesn’t meet your needs gives you a second chance to correct course. However, the one-change limit means choosing carefully—if you switch during OEP, you’re locked in until the next AEP unless you qualify for a Special Enrollment Period through circumstances like moving or losing other coverage.

Preventing Future Mistakes

Set yourself up for success during future enrollment periods:

• Create a Medicare file containing ANOCs, plan documents, provider lists, and prescription records
• Schedule an annual October review with a licensed Medicare advisor
• Update your prescription list quarterly, noting any additions or changes
• Track your actual healthcare utilization to improve future plan selection
• Set calendar reminders for AEP starting September 1

Frequently Asked Questions

Can I change my Medicare plan after December 7?

If you’re in a Medicare Advantage plan, you have one opportunity to change during the Medicare Advantage Open Enrollment Period (January 1–March 31). You can switch to a different MA plan or return to Original Medicare with Part D. After March 31, you need a qualifying Special Enrollment Period event like moving or losing other coverage to make changes outside the annual AEP.

What happens if I ignore my Annual Notice of Change?

You automatically renew in your current plan with all the changes detailed in the ANOC. This can mean higher premiums, reduced benefits, different copays, formulary changes affecting your medications, or provider network modifications. You won’t have coverage gaps, but you may face unexpected costs or lose access to preferred providers without realizing until you need care.

How do I know if my medications are covered next year?

Check your plan’s formulary (drug list) in the ANOC or online through your plan’s website. Medicare’s Plan Finder tool at Medicare.gov also allows you to enter your medications and see which plans cover them and at what cost tier. Verify both coverage and tier status—a drug might remain covered but move from Tier 2 to Tier 4, significantly increasing your copay.

Should I switch Medicare plans every year?

Not necessarily. You should review your plan annually, but only switch if changes make your current plan less suitable or if better alternatives exist. If your plan still covers your medications affordably, includes your providers, and meets your needs at reasonable cost, staying put makes sense. However, ignoring the annual review means missing opportunities for improvement or failing to notice disadvantageous changes.

What is the Part D late enrollment penalty?

If you go without creditable prescription drug coverage after becoming eligible for Medicare Part D, you face a permanent penalty of 1% of the national base beneficiary premium for each month you were eligible but uncovered. This penalty compounds and continues for as long as you have Part D coverage. A five-month gap results in approximately 5% permanently higher premiums—for life.

Conclusion

Avoiding Medicare open enrollment mistakes in 2026 requires proactive engagement rather than passive acceptance. The common thread among the costliest errors—ignoring ANOCs, skipping prescription reviews, failing to verify networks, procrastinating until December, assuming uniform spousal needs, and focusing solely on premiums—is inaction or incomplete evaluation. These mistakes result in thousands of dollars in unnecessary expenses, coverage gaps, and frustration that persists throughout the year.

For Lawrence, KS residents currently dealing with enrollment mistakes made during the 2025 AEP, remember that the Medicare Advantage Open Enrollment Period offers a correction opportunity through March 31, 2026. For everyone planning ahead, mark your calendars for the next Annual Enrollment Period beginning October 15, 2026. Start your review early, read your ANOC thoroughly, verify networks and formularies, calculate total costs beyond just premiums, and evaluate each household member’s needs individually.

Medicare enrollment doesn’t have to be overwhelming. With proper preparation, realistic timelines, and thorough comparison of available options, you can select coverage that truly serves your health needs and budget. Whether you need assistance navigating current coverage issues or want to plan ahead for the next enrollment period, working with knowledgeable advisors familiar with Douglas County healthcare networks and Kansas plan options ensures you avoid the common pitfalls that affect so many beneficiaries annually.

Medicare Disclaimer: This information is for educational purposes and does not constitute medical or insurance advice. Medicare rules and plan offerings change annually. Contact Medicare at 1-800-MEDICARE or work with a licensed insurance advisor for personalized guidance based on your specific situation.

Sources and References

• Centers for Medicare & Medicaid Services – www.cms.gov
• Medicare.gov Official Site – www.medicare.gov
• Medicare Plan Finder Tool – Medicare.gov
• Annual Notice of Change (ANOC) Requirements – CMS Guidelines