If you hit your $2,100 Part D out-of-pocket threshold sometime this year, you’ve probably gotten used to paying nothing for your covered prescriptions. So what happens if your plan changes its formulary in October, right before you’re counting on that $0 copay to carry you through December?
For many beneficiaries in Dallas and Fort Worth, this question isn’t hypothetical. Mid-year tier shifts and formulary adjustments happen every year, and understanding how they work, especially once you’ve already reached your out-of-pocket cap, is the difference between keeping your savings intact and getting an unpleasant surprise at the pharmacy counter.
This guide walks through what mid-year tier shifts actually are, why your $0 catastrophic coverage has one important limit, and what to do if your plan changes the rules partway through the year.
What Mid-Year Tier Shifts Actually Are
Every Medicare Part D plan and Medicare Advantage plan with drug coverage organizes its covered medications into a formulary, a list sorted into cost tiers. Moving a drug to a higher tier, or adding a new restriction like step therapy or prior authorization, is what’s commonly called a tier shift.
Federal rules, laid out in 42 CFR § 423.120, limit when and how plans can make these changes.
Generally speaking, mid-year formulary changes fall into two categories:
Maintenance changes, which include switching to a generic version of a brand-name drug, adding a new coverage restriction, or updating the formulary based on new FDA safety guidance. Plans generally must give you 60 days’ notice or a 60-day transition refill before these take effect.
Non-maintenance changes, which cover most other negative formulary changes. If you’re already taking an affected drug, your plan generally has to let you keep taking it for the rest of the plan year, as long as it’s medically necessary, and send you a notice explaining the exemption.
There’s one exception worth knowing: if the FDA declares a drug unsafe and pulls it from the market, your plan can remove it immediately, without the standard notice period.
This year carries a bit more formulary activity than usual. The first prices negotiated under Medicare’s Drug Price Negotiation Program took effect on January 1, 2026, for ten selected medications, and plans generally must include those drugs on their formularies going forward, with only limited exceptions such as replacing one with a newly available generic. That’s part of why 2026 has been a more active year than usual for formulary updates.
Here’s what this can look like in practice. Say your plan sends a mid-year notice that your brand-name cholesterol medication is being moved because a generic equivalent just became available. That’s a maintenance change, so you should get 60 days’ notice or a transition refill while you and your doctor decide whether to switch to the generic or request an exception to stay on the brand-name version. Either way, you have time to react instead of being caught off guard at the counter.
The $2,100 Catastrophic Phase Has One Important Catch
Once your true out-of-pocket spending on covered drugs reaches $2,100 in 2026, you enter what’s called the catastrophic coverage phase. From that point through December 31, you pay $0 for your plan’s covered Part D drugs, according to KFF’s snapshot of the Part D benefit.
Here’s the part that catches people off guard: that $0 copay only applies to drugs on your plan’s formulary. According to the Center for Medicare Advocacy, non-formulary drugs don’t count toward this protection at all. If your plan removes a drug you take, or you need a medication that was never on the formulary, you’re responsible for the full retail cost, even after reaching your $2,100 cap.
This matters most for beneficiaries who reached the threshold mid-year. A tier shift or formulary change that happens in September or October could mean the medication that got you to $0 copays is suddenly billed at full price for the remaining months, right when you were counting on that protection the most.
Consider a beneficiary who reached the $2,100 threshold in August after several months of specialty drug copays. If that same drug is removed from the formulary in October, the $0 catastrophic benefit no longer applies to it. Instead of finishing the year paying nothing, that beneficiary could be facing the medication’s full retail price for the last two months of the plan year, unless a formulary exception is approved in time.
Protecting Your Savings If Your Formulary Shifts
If you get a notice that your plan is changing coverage for a drug you take, a few steps can help you avoid losing your out-of-pocket protection:
- Read the notice carefully. It should tell you whether the change is a maintenance change, and whether you qualify for a transition refill or an exemption for the rest of the year.
- Ask your pharmacist to confirm the drug’s current tier and whether it’s still on the formulary before you refill. Pharmacists can often see formulary updates before a mailed notice arrives.
- Request a formulary exception if your medication is no longer covered. Your plan doesn’t have to approve it automatically, and if approved, the drug is often placed on a higher specialty tier, but it’s the only path back to formulary status, and the coverage that comes with it.
- Appeal a denied exception if your doctor believes the formulary alternatives aren’t appropriate for your condition. You have the right to appeal, and your doctor’s input matters in that process.
- Keep a paper trail of every notice, call, and pharmacist conversation. If a charge looks wrong later, this record makes it easier to sort out.
None of this means your plan did anything improper. Formularies are required to change periodically to reflect new generics, new safety data, and new drug approvals. The goal here isn’t to second-guess your plan, it’s to make sure a routine update doesn’t quietly cost you money you didn’t expect to pay.
Getting Ready for the 2027 Open Enrollment Window
The Annual Enrollment Period runs October 15 through December 7 each year, and it’s your main opportunity to switch plans if a mid-year tier shift left you unhappy with your current formulary.
Before this year’s window closes, it helps to:
- Pull your full medication list, including dosage and frequency, so you can compare it against next year’s formularies
- Note which drugs, if any, were affected by a tier shift or coverage restriction this year
- Compare how each plan you’re considering handles those same medications for 2027
- Ask whether a plan’s specialty tier cost-sharing changed, since that’s where formulary exceptions often land
If you’re comparing Medicare Advantage plans in Fort Worth or in Dallas for the upcoming year, this is also the moment to confirm that any plan you’re considering actually covers the medications that matter most to you, rather than assuming this year’s coverage will carry over unchanged.
Making Sure Your Part D Savings Actually Last
At Medicare4USA, we spend a lot of time helping beneficiaries make sense of exactly this kind of mid-year change. Whether you’re working with a Medicare agent in Dallas or a Medicare agency in Fort Worth, the goal is the same: making sure the $0 catastrophic protection you worked to reach actually applies to the medications you need for the rest of the year.
We’ll walk through your current formulary, flag any tier shifts that might affect your specific prescriptions, and help you compare options before the 2027 Annual Enrollment Period closes on December 7. A formulary notice in the mail doesn’t have to mean guesswork on your end, we can help you read it, respond to it, and decide whether a formulary exception or a plan change makes more sense for your situation.
Contact us today, and let’s make sure your out-of-pocket savings are protected through the rest of this plan year and into the next.