6 Medicare Annual Enrollment Mistakes to Avoid in 2026

The Medicare Annual Enrollment Period, which runs from October 15 through December 7 each year, is the one window most beneficiaries have to review and change their coverage. Despite its importance, many people miss out on the opportunity to reduce costs or improve their benefits because of avoidable mistakes.

In 2026, the stakes are higher than in previous years. The federal program that has kept Part D premiums artificially low is ending, which means drug plan costs could rise significantly for 2027. That makes this year's AEP more consequential than most. Below are the six most common and costly mistakes beneficiaries make during the Annual Enrollment Period, along with clear guidance on how to avoid each one.

Mistake 1: Auto-Renewing Without Reviewing Your Plan

Many Medicare beneficiaries let their current plan renew automatically without comparing it to other available options. The assumption is that if a plan worked well last year, it will continue to meet their needs. That assumption is often wrong. Plans can and do change their premiums, deductibles, benefits, and provider networks every single year.

Your insurer is required to mail you an Annual Notice of Change by September 30. This document outlines every change your plan is making for the upcoming year. If you do not read it before the AEP opens on October 15, you could end up with higher costs, a narrower provider network, or reduced benefits without realizing it until you need care.

Mistake 2: Not Checking Your Prescription Drug Coverage

Failing to review your prescription drug coverage is one of the most expensive mistakes a beneficiary can make. Part D drug plans change their formularies every year. A medication that was on Tier 2 last year may be moved to Tier 4, subject to prior authorization, or removed from coverage entirely. Assuming your prescriptions will continue to be covered at the same cost is a gamble that frequently does not pay off.

It is equally important to confirm that your preferred pharmacy remains in-network. Drug plans negotiate separate contracts with pharmacies, and those contracts can change. A plan that offered preferred pricing at your local pharmacy last year may no longer do so in 2027. The difference in cost between a preferred and non-preferred pharmacy can be substantial over the course of a year.

The Medicare Plan Finder tool at Medicare.gov allows you to enter your specific medications and compare actual out-of-pocket costs across all Part D plans available in your area. This is the most reliable way to verify coverage and cost before re-enrolling.

Mistake 3: Overlooking Medicare Advantage Changes

Medicare Advantage (Part C) plans can offer attractive benefits like dental, vision, hearing, and gym memberships. But these benefits are subject to change every year. Plans can update their premiums, cost-sharing, provider networks, and covered services annually. If you do not review your plan, you may miss changes that affect your access to care or your out-of-pocket costs.

In 2026, CMS reduced the number of Medicare Advantage plans available in many counties as part of a broader effort to improve plan stability. Some insurers also implemented new prior authorization requirements for certain services. These changes make it more important than ever to verify that your preferred doctors and specialists are still in-network before the AEP closes.

Before committing to the same plan, take time to explore all Medicare Advantage options available in your area. Compare premiums, maximum out-of-pocket limits, provider access, and added benefits to ensure you are still enrolled in the most cost-effective and comprehensive plan for your needs.

Mistake 4: Ignoring All Your Coverage Options

Many people believe that the Annual Enrollment Period is only about switching Medicare Advantage plans. That is not the case. During the AEP, you can also switch from Medicare Advantage back to Original Medicare, add or change a Part D drug plan, or drop Medicare Advantage entirely and pair Original Medicare with a Medigap supplement plan. By not exploring all your options, you may be leaving better coverage or lower costs on the table.

One important nuance: if you switch from Medicare Advantage back to Original Medicare during the AEP, you will need to apply for a Medigap plan separately. In most states, insurers can use medical underwriting for Medigap applicants outside of the initial Medigap open enrollment period, which means you could be charged higher premiums or denied coverage based on your health history. This is a critical consideration that many beneficiaries are unaware of.

If you are overwhelmed by the options, working with a licensed Medicare agent can help you understand what is available in your area and which combination of coverage best fits your health needs and budget. There is no cost to you for this guidance.

Mistake 5: Missing the Enrollment Deadline

Missing the December 7 deadline is one of the most consequential mistakes a Medicare beneficiary can make. If you do not act by this date, you will be locked into your current plan for the full year unless you qualify for a Special Enrollment Period. That could mean staying in a plan that is no longer affordable or no longer covers your needs adequately.

There is one exception worth knowing: the Medicare Advantage Open Enrollment Period runs from January 1 through March 31 each year. During this window, you can switch from one Medicare Advantage plan to another, or drop Medicare Advantage and return to Original Medicare. However, you cannot use this period to switch from Original Medicare to Medicare Advantage, and you cannot add or change a standalone Part D plan unless you are also switching to Original Medicare. It is a limited backup option, not a substitute for acting during the AEP.

Mistake 6: Not Planning for 2027 Part D Changes

This is a new mistake that did not exist in prior years, and it is specific to the 2026 AEP. The federal government has been running a program called the Medicare Part D Premium Stabilization Demonstration, which has subsidized Part D premiums since 2024 to prevent large premium spikes after the Inflation Reduction Act restructured how drug plan costs are shared between the government and insurers.

That subsidy program is ending. CMS announced it will not renew the demonstration for 2027, which means Part D premiums will no longer be artificially held down. Analysts estimate that average standalone Part D premiums could increase by $10 to $20 per month or more for 2027. For beneficiaries currently enrolled in low-premium plans, the jump could be even larger.

The 2026 AEP is the enrollment window that determines your Part D coverage for 2027. When you compare drug plans this fall, pay close attention to the 2027 premium listed for each plan, not just the current year cost. A plan that looks affordable today may look very different when the subsidy is gone. Our full breakdown of this change is available in our article on the Medicare Part D subsidy ending in 2027.

Key Dates for the 2026 AEP

Make the Most of Your 2026 Enrollment

Avoiding these mistakes during the 2026 Medicare Annual Enrollment Period can help you secure the best coverage for the year ahead and protect yourself from the Part D premium increases coming in 2027. Do not assume your current plan is still the right fit. Read your Annual Notice of Change, verify your drug coverage, check your provider network, and explore all available options before December 7.

If you are unsure where to start, our licensed agents can walk you through your options at no cost to you. Use the button below to get matched with plans in your area and see what is available before the AEP closes.

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