- Plans can change tiers each January, but mid-year tier increases are tightly limited — and they owe you 60 days' advance written notice.
- If your drug moves up a tier or off the formulary, you can request a tier exception, ask for a formulary exception, or switch to a covered alternative.
- Reading your Annual Notice of Change each fall and checking tiers on Medicare Plan Finder prevents most tier surprises.
Last month your prescription cost $20. This month the pharmacist says it's $85 — your Part D plan moved it to a higher tier, or dropped it from the formulary entirely. It feels arbitrary, but Medicare sets specific rules about when and how plans can make these changes. Here's what happened and what you can do about it.
Why tiers change every January
Part D formularies — the lists of covered drugs and their tiers — are not permanent. Every plan renegotiates its drug list for the coming plan year, and changes take effect each January 1. Common reasons include:
- A generic became available. When a brand drug loses exclusivity, plans typically drop the brand or push it to a high tier while covering the generic cheaply.
- Rebate negotiations changed. Plans negotiate prices with drugmakers every year. A drug that got a worse deal this year can be demoted a tier.
- Clinical guidelines shifted. New evidence about which drug works best for a condition can move one product to a preferred tier and another off it.
Your plan must mail you an Annual Notice of Change (ANOC) each fall, listing every change for next year — including tier changes to your medications. Many people recycle it unopened. That's where tier surprises come from.
When plans can change tiers mid-year
Medicare strongly favors formulary stability, so plans are limited in what they can do after January 1. The rules:
- Improvements are always allowed. A plan can add a drug to its formulary, lower a drug's tier, or drop a prior authorization requirement at any time during the year.
- Negative changes are restricted. Plans generally may not remove a drug or raise its tier mid-year, except in narrow cases — a new generic equivalent becomes available, new safety information emerges, or the drug is withdrawn from the market.
- Therapeutic categories are locked. Plans can't reshuffle whole drug classes mid-year; those changes happen only at the start of the plan year.
So if your drug jumped from Tier 2 to Tier 3 in May, the likely explanation is a new generic of your brand (an allowed "generic substitution" change) or new safety concerns.
Your rights: the 60-day notice rule
When a plan makes a mid-year change that raises your tier or removes your drug, Medicare rules generally require the plan to give affected enrollees 60 days' advance written notice — plus notifying your prescriber, network pharmacies, and CMS. The notice must explain what changed, when it takes effect, and how to request a formulary exception.
Practically, this means you should not discover a tier change at the pharmacy counter — the plan is supposed to tell you first. If you were blindsided, check whether the notice went to an old address or an email you don't check, and then call the plan's member services line to confirm the change and your options.
What to do when your drug moves up a tier
You have several options, and the right one depends on your situation:
- Ask your doctor about a covered alternative. If your drug moved because a new generic exists, the generic is usually on Tier 1 with the lowest copay.
- Request a tier exception. If the lower-tier alternative won't work for you medically, your doctor can submit a tiering exception request with a statement explaining why the cheaper alternative isn't medically appropriate for you.
- Request a formulary exception. If the drug was removed entirely, a formulary exception can restore coverage. Expedited requests are available when your health is at risk.
- Ask for a transition fill. You may be entitled to a one-time transition supply (typically 30 days) of the drug while the exception is being decided.
- Compare plans. If your plan keeps moving your drugs upward, switch during the Annual Enrollment Period (October 15 – December 7). Medicare Plan Finder lets you enter your exact medications and see which plans cover them on which tier.
Keep notes on every plan call — dates, names, and reference numbers for exception requests. Part D appeals have five levels, and you'll need the paperwork if you escalate.
How to avoid tier surprises next year
- Read the Annual Notice of Change when it arrives in the fall — check the drug list against your prescriptions before enrollment closes.
- Re-run Medicare Plan Finder during Open Enrollment with your full medication list, pharmacy, and delivery method. A plan that was cheapest last year may not be cheapest this year.
- Ask your doctor early. If a drug is moving to a high tier, your doctor may already know a preferred alternative — or may have samples to bridge a gap.
- Watch your out-of-pocket math. In 2026, costs on covered drugs are capped at $2,100 for the year, after which you pay $0 for covered prescriptions. A tier increase hurts most early in the year, but if you're heading toward the cap anyway, staying on the drug through Part D may still beat switching.
Bottom line: Tier changes usually happen in January when plans renegotiate their drug lists, mid-year increases are limited to cases like new generics or safety issues and require 60 days' notice — so read your Annual Notice of Change, ask your doctor about covered alternatives, and don't hesitate to request a tier exception if the cheaper drug won't work for you.