Medicare Open Enrollment: How to Choose the Right Plan Each Year

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Meta Description: Medicare Open Enrollment runs Oct 15-Dec 7. Learn how to review your plan, compare costs, avoid costly mistakes, and choose the right Medicare coverage each year.

Featured Image Description: A couple in their mid-60s sitting at a kitchen table with a laptop open to the Medicare.gov Plan Finder tool, reviewing paperwork and comparing Medicare plan options together. Warm natural lighting, organized but realistic setting with reading glasses and a coffee mug nearby. Alt text: Retired couple reviewing Medicare plan options on a laptop during open enrollment period

Every October, Medicare sends you an Annual Notice of Change letter. And every October, millions of retirees toss that letter into a drawer without reading it.

Consider a hypothetical: Patricia, 71, kept the same Medicare Advantage plan for three consecutive years without reviewing it once. When she finally sat down and compared her coverage to what was currently available, she discovered her monthly premiums had crept up by $87, her preferred cardiologist had quietly left the network, and one of her maintenance medications had moved to a higher formulary tier. All told, she was paying roughly $2,400 more per year than she needed to for comparable coverage., her preferred cardiologist had quietly left the network, and one of her maintenance medications had moved to a higher formulary tier. All told, she was paying roughly $2,400 more per year than she needed to for comparable coverage.

Patricia’s story is not unusual. It is, in fact, one of the most common and most preventable mistakes I see in retirement planning. The good news is that Medicare gives you a window every year to fix it.

What Is Medicare Open Enrollment?
What You Can Change During Open Enrollment
Annual Enrollment Period vs. Medicare Advantage Open Enrollment Period
Your Step-by-Step Plan Review Checklist
How to Compare Plans Using Medicare.gov Plan Finder
When Switching From Medicare Advantage Back to Original Medicare Makes Sense
The Medigap Trap: What You Could Lose by Switching
A Cost Comparison Framework That Actually Works
How Prescription Drug Changes Affect Your Plan Choice
Common Open Enrollment Mistakes to Avoid

What Is Medicare Open Enrollment?

Medicare Open Enrollment — officially called the Annual Enrollment Period (AEP) — runs from October 15 through December 7 every year. Any changes you make during this window take effect on January 1 of the following year.

This is the one time each year when nearly every Medicare beneficiary can make changes to their coverage without needing a Special Enrollment Period or qualifying life event. According to CMS.gov, more than 65 million Americans are eligible to review and adjust their Medicare coverage during this period.

Think of it as your annual healthcare reset button. Whether you are on Original Medicare with a standalone Part D plan, enrolled in a Medicare Advantage plan, or considering a switch between the two, this is your opportunity.

Thomas’ Take: Treat October 15 like Tax Day for your healthcare. Mark it on your calendar. Set a reminder. The stakes are too high to let it slip by. Mark it on your calendar. Set a reminder. The stakes are too high to let it slip by.

What You Can Change During Open Enrollment

During the AEP, you have broad flexibility to restructure your Medicare coverage. Here is what is on the table:

Switch from Original Medicare to a Medicare Advantage plan (or vice versa)
Switch from one Medicare Advantage plan to a different Medicare Advantage plan
Join a Medicare Part D prescription drug plan
Switch from one Part D plan to another Part D plan
Drop your Part D coverage entirely (though this can trigger a late enrollment penalty later)

What you generally cannot do during the AEP is purchase a new Medigap (Medicare Supplement) policy with guaranteed issue rights — unless you are within your Medigap Open Enrollment Period or qualify for a specific guaranteed issue situation. This distinction matters enormously, and I will explain why in the Medigap Trap section below.

If you are weighing whether Original Medicare plus a supplement or a Medicare Advantage plan is the better fit, I walk through that decision in detail in my post on Medigap vs. Medicare Advantage: Which Is Right for Your Retirement?.

Annual Enrollment Period vs. Medicare Advantage Open Enrollment Period

This is where things get confusing, and understandably so. There are actually two distinct enrollment windows, and they serve different purposes.

Annual Enrollment Period (AEP): October 15 — December 7 This is the main open enrollment window. Everyone on Medicare can make changes. Changes take effect January 1.

Medicare Advantage Open Enrollment Period (MA OEP): January 1 — March 31 This secondary window is exclusively for people who are already enrolled in a Medicare Advantage plan as of January 1. During the MA OEP, you can:

Switch to a different Medicare Advantage plan
Drop your Medicare Advantage plan and return to Original Medicare (and enroll in a standalone Part D plan)

You cannot use the MA OEP to go from Original Medicare into a Medicare Advantage plan. That is a one-way street during this period.

The MA OEP exists as a safety net. If you made a change during the AEP and your new plan is not working out — maybe the network is smaller than you expected, or a provider you need is not covered — you have until March 31 to course-correct. Changes made during the MA OEP take effect the first of the month after the plan receives your request.

For a complete breakdown of all the enrollment windows and deadlines, see my guide on Medicare Enrollment Deadlines You Cannot Afford to Miss.

Your Step-by-Step Plan Review Checklist

Every September, you should receive your plan’s Annual Notice of Change (ANOC) and Evidence of Coverage (EOC) documents. These outline exactly what is changing for the upcoming year. Here is a systematic way to review them.

In-article image description: A clean checklist infographic with six items — formulary changes, premium changes, network changes, star ratings, out-of-pocket maximums, and coverage gaps — each with a simple icon and one-line description. Alt text: Medicare open enrollment plan review checklist covering six key areas to evaluate

1. Formulary Changes

Has your plan moved any of your current medications to a higher tier? Have any drugs been removed from the formulary entirely? Even small tier changes can add hundreds of dollars per year.

2. Premium Changes

What is the new monthly premium? Compare it not just to this year, but to competing plans in your area.

3. Network Changes

Are your current doctors, specialists, and preferred hospital still in-network? For Medicare Advantage plans, this is critical. A plan with a low premium means nothing if your oncologist is no longer covered.

4. Star Ratings

Medicare assigns each plan a star rating from 1 to 5. Plans with 4+ stars tend to offer better outcomes and sometimes bonus benefits. Check the Medicare.gov Plan Finder for current ratings.

5. Out-of-Pocket Maximum Changes

Has the plan’s maximum out-of-pocket (MOOP) limit changed? A lower premium with a higher MOOP could cost you more in a year with significant medical needs.

6. Coverage Gaps and Additional Benefits

For Medicare Advantage plans, review dental, vision, hearing, and wellness benefits. These extras vary wildly between plans and change frequently.

Pro Tip: Create a simple spreadsheet with your current plan’s key numbers in one column and each competing plan in adjacent columns. Seeing everything side by side makes the decision dramatically clearer.

How to Compare Plans Using Medicare.gov Plan Finder

The Medicare Plan Finder tool is free, comprehensive, and — once you know how to use it — genuinely helpful. Here is how to get the most out of it.

Step 1: Gather your information. You will need your Medicare number or ZIP code, a list of your current prescriptions (including dosages), and the names of your preferred doctors and pharmacies.

Step 2: Enter your drugs. The Plan Finder will show you estimated annual drug costs for each plan based on your specific medications. This is where most of the real savings hide.

Step 3: Filter and compare. You can filter by plan type (Medicare Advantage, Part D, Medigap in some states), then compare up to three plans side by side. Pay attention to total estimated annual costs — not just the monthly premium.

Step 4: Check provider directories. For Medicare Advantage plans, verify that your doctors are in-network by checking the plan’s online provider directory and calling your doctor’s office to confirm. Directories can be outdated.

Step 5: Review star ratings and complaints. Higher-rated plans have been independently evaluated for quality of care, member satisfaction, and customer service.

The Kaiser Family Foundation’s Medicare resources are also excellent for understanding broader trends in plan availability and costs each year.

When Switching From Medicare Advantage Back to Original Medicare Makes Sense

Medicare Advantage plans can be excellent — many retirees are very happy with theirs. But there are situations where switching back to Original Medicare with a Medigap supplement and standalone Part D plan becomes the smarter move.

Your health needs have changed. If you have been diagnosed with a complex or chronic condition requiring specialists across multiple health systems, Original Medicare’s lack of network restrictions can be invaluable.

You travel frequently or split time between states. Medicare Advantage networks are typically regional. Original Medicare is accepted by virtually any provider nationwide that takes Medicare.

Your plan’s network has shrunk. If key providers have left your plan’s network, you may be paying for access you no longer have.

Out-of-pocket costs are climbing. Medicare Advantage plans have out-of-pocket maximums, but those maximums can be $7,000 or more. A Medigap Plan G, by contrast, covers nearly all of your cost-sharing under Original Medicare, creating much more predictable expenses.

The MA OEP (January 1 — March 31) gives you one path back. But before you make this switch, read the next section carefully.

The Medigap Trap: What You Could Lose by Switching

This is one of the most important and least understood aspects of Medicare planning. I cannot stress it enough.

When you first enroll in Medicare Part B, you have a six-month Medigap Open Enrollment Period during which insurance companies must sell you any Medigap policy they offer, regardless of your health, at the standard rate. This is your guaranteed issue right.

Once that window closes, those protections largely disappear.

If you switch from Original Medicare to a Medicare Advantage plan, stay for a few years, and then decide to switch back, you may no longer have guaranteed issue rights for a Medigap policy. In most states, insurers can:

Deny your application based on health conditions
Charge you significantly higher premiums through medical underwriting
Exclude coverage for pre-existing conditions

There are some limited guaranteed issue situations — for example, if you switch back within 12 months of first joining a Medicare Advantage plan. But the protections are narrow and state-specific.

Thomas’ Take: It’s a common pattern: someone who was perfectly healthy at 65 switches to Medicare Advantage, develops health issues in their 70s, and then finds themselves unable to get affordable Medigap coverage when they want to switch back. This is a one-way door for many people. Understand it before you walk through it. This is a one-way door for many people. Understand it before you walk through it.

A handful of states — including New York, Connecticut, and Massachusetts — require guaranteed issue for Medigap policies year-round. North Carolina, for example, does not. Know your state’s rules.

A Cost Comparison Framework That Actually Works

Raw premium numbers can be misleading. Here is a framework that gets you to a true apples-to-apples comparison:

Hypothetical Example: Margaret, Age 68, Charlotte, NC

Margaret takes three medications (lisinopril, atorvastatin, and Eliquis), sees a cardiologist twice a year, and has one primary care visit every quarter. Let’s compare two options.

Cost Category	Medicare Advantage Plan A	Original Medicare + Medigap G + Part D Plan
Monthly Premium	$28	$198 (Medigap $162 + Part D $36)
Annual Premium	$336	$2,376
Part B Premium	$185/mo ($2,220/yr)	$185/mo ($2,220/yr)
Estimated Drug Costs	$1,840/yr	$1,120/yr
Specialist Copays (est.)	$280/yr	$0 (covered by Medigap)
Annual Physical/PCP	$0	$0
Max Out-of-Pocket Risk	$7,550	~$250 (Part B deductible)
Total Estimated Annual Cost	$4,676	$5,716
Worst-Case Scenario Cost	$12,226	$5,966

In a healthy year, Margaret saves about $1,040 with Medicare Advantage. But in a year with a hospitalization or major medical event, Original Medicare with Medigap could save her more than $6,000.

This is why I always tell clients to evaluate both the expected cost and the worst-case cost. Your risk tolerance and health trajectory should drive the decision.

Note that if Margaret is subject to IRMAA surcharges based on her income, both her Part B and Part D premiums could be meaningfully higher, affecting this math in both scenarios.

Pro Tip: Run this comparison every year. Drug costs, premiums, and plan structures change annually. A plan that was the best value last year may not be the best value next year.

How Prescription Drug Changes Affect Your Plan Choice

Prescription drugs are often the single biggest variable in Medicare plan costs from year to year. Here is why.

Formulary tier changes can move a brand-name drug from a preferred tier ($40 copay) to a non-preferred tier ($95 copay) overnight. Multiply that by 12 months and you have an extra $660 per year for one medication.

New generics entering the market can make one plan dramatically cheaper than another if that plan has already added the generic to its formulary.

The Part D coverage gap (sometimes called the donut hole) was largely eliminated for brand-name drugs under the Inflation Reduction Act, and the $2,000 annual out-of-pocket cap on Part D spending that took effect in 2025 has been a meaningful change. But plan-specific costs — copays, coinsurance, and tier placement — still vary widely.

Step therapy and prior authorization requirements differ between plans. One plan might cover a medication immediately while another requires you to try (and fail on) a cheaper alternative first.

When comparing plans, always enter your complete, current medication list into the Medicare Plan Finder. Do not guess. The difference between plans can easily be $1,000 or more per year based on drug costs alone.

Common Open Enrollment Mistakes to Avoid

Here are the open enrollment mistakes that come up most often:

Mistake 1: Doing nothing. The most expensive decision is often no decision at all. Plans change every year. Your health changes. The landscape of available plans in your ZIP code changes. Autopilot is not a strategy.

Mistake 2: Choosing based on premium alone. A $0 premium Medicare Advantage plan can end up costing far more than a $45/month plan if the formulary, network, or out-of-pocket limits are worse for your specific situation.

Mistake 3: Ignoring the Annual Notice of Change. Your plan is legally required to tell you what is changing. Read the ANOC. It takes 15 minutes and could save you thousands.

Mistake 4: Assuming your doctors are still in-network. Provider networks change every year. Always verify — do not rely on last year’s information.

Mistake 5: Not accounting for upcoming health needs. If you know a surgery or new treatment is likely in the coming year, factor that into your plan comparison. A plan that looks cheap in a healthy year could be very expensive in a year with significant utilization.

Mistake 6: Missing the deadline. December 7 is firm. If you miss it, you are generally locked into your current plan (or lack thereof) until the next enrollment period, with limited exceptions.

Mistake 7: Overlooking Extra Help and Low-Income Subsidies. If your income and resources are limited, you may qualify for programs that significantly reduce your Part D costs. Check Medicare.gov’s Extra Help page to see if you qualify.

Key Takeaways

Review your Medicare coverage every year during the Annual Enrollment Period (October 15 — December 7). Plans change annually, and the best plan last year may not be the best plan this year.
Compare total estimated annual costs, not just monthly premiums. Factor in drug costs, copays, deductibles, and out-of-pocket maximums for a true comparison.
Understand the Medigap trap before switching to Medicare Advantage. Leaving Original Medicare could mean losing guaranteed issue rights for supplemental coverage — a decision that is difficult or impossible to reverse if your health changes.
Use the Medicare.gov Plan Finder with your actual medications and doctors to get personalized cost estimates rather than relying on generic plan summaries.
Consider both your expected costs and worst-case costs. Your risk tolerance and anticipated health needs should be central to your decision.

Frequently Asked Questions

Can I change my Medicare plan outside of the Annual Enrollment Period?

In most cases, no. The AEP (October 15 — December 7) is the primary window. However, if you qualify for a Special Enrollment Period — due to moving, losing employer coverage, qualifying for Medicaid, or certain other life events — you may be able to make changes outside the AEP. The Medicare Advantage Open Enrollment Period (January 1 — March 31) also allows current MA enrollees to make one plan switch.

What happens if I miss the December 7 deadline?

You will generally remain in your current plan for the following year. If you are in a Medicare Advantage plan, you can still make one change during the MA OEP (January 1 — March 31). But if you are on Original Medicare and wanted to switch Part D plans or join a Medicare Advantage plan, you will typically need to wait until the next AEP.

Is there any cost to use the Medicare Plan Finder or switch plans?

No. Using the Medicare Plan Finder at Medicare.gov is completely free, and there is no fee charged by Medicare for switching plans during an enrollment period. Be cautious of anyone charging you a fee for help with Medicare enrollment — licensed insurance agents and State Health Insurance Assistance Programs (SHIPs) provide this help at no cost.

Should I work with an insurance broker or do this on my own?

Both approaches can work. The Medicare Plan Finder is robust enough for many people to compare plans independently. However, a knowledgeable Medicare insurance broker can be helpful if you have complex health needs, take many medications, or find the process overwhelming. Brokers are typically compensated by the insurance companies, not by you. Just be aware that brokers can only show you plans from the companies they represent.

Next Steps

Medicare open enrollment does not have to be stressful, but it does require your attention. Fifteen to thirty minutes of focused plan review each fall can save you hundreds — sometimes thousands — of dollars and ensure you have the coverage that actually fits your life.

For more on retirement income, bucket planning, and Social Security claiming, browse the retirement planning archive or sign up for the weekly newsletter at the bottom of any page.

Your healthcare coverage is too important to leave on autopilot.

This article is published by Confluence Media Group LLC, an independent publisher of educational financial content. Thomas Clark is a Series 65 Investment Advisor Representative. The information provided is for educational and informational purposes only and is not personalized financial, tax, or legal advice. Past performance does not guarantee future results. All investing involves risk, including potential loss of principal. Consult a qualified professional before making financial decisions.

Confluence Media Group LLC is a separate entity from Confluence Capital Management, the investment advisory practice through which Thomas Clark provides advisory services. Advisory services are not offered through this publishing platform.

Thomas Clark

Thomas Clark is a Series 65 licensed investment advisor and experienced trader. He specializes in investing, retirement planning, and market analysis, helping individuals build wealth and make informed financial decisions.