When Your Part D Plan's Drug List Changes: Formulary Changes, Notices, and Your Options

Your Part D plan has a list of drugs it covers. That list is called a formulary. The list can change during the year. A change can raise what you pay for a drug you take each day. It can also add a step you must do before the plan pays. This guide shows what kinds of changes can occur, what notice you should get, and what you can do next. Our paying for care hub holds more guides on drug costs and plan rules.

What a drug list is

Each Part D plan makes its own drug list. The list groups drugs into tiers. Low tiers tend to cost less. High tiers tend to cost more. But the tier alone does not set your cost.

Read that rule again, as it is the key point of this guide. A tier is not a price: the plan's own cost for that drug is what the member pays. Two drugs on the same tier can cost you two sums that are not the same. Two plans can charge two sums for the same drug on the same tier.

Our guide on Part D tier levels shows how tiers work and how to find your true cost. You can also browse drug guides in our medications hub.

The list also shows rules for each drug. A rule may say the plan must approve the drug first. A rule may say you must try a like drug first. A rule may limit how much you can get at one time.

What can change mid-year

Plans do not keep the list fixed all year. A plan can make changes during the year. The most common changes are these:

That last change can be good news. A generic drug has the same active drug as the brand drug. It often costs less. But the switch can still feel like a shock if you learn of it at the drug store. The plan must follow notice rules for this kind of swap, just as it does for other changes.

A plan may also add a drug to the list. That kind of change does not hurt you, and the plan may not send a notice for it.

• A drug moves to a higher tier, so your cost goes up.
• A drug moves to a lower tier, so your cost goes down.
• The plan adds a rule that says it must approve the drug first. This is called prior authorization.
• The plan adds a step rule. You must try a like drug first, and it must not work for you, before the plan pays for the first drug. This is called step therapy.
• The plan takes a drug off the list, so it no longer covers that drug.
• A generic drug takes the place of a brand drug on the list.

What notice you should get

If a change hits a drug you take now, the plan sends you a notice. The notice tells you what will change and when it will start. It also tells you what you can do.

Keep each notice you get. Put it with your drug list and your plan card. Bring it to your next visit or call with your doctor.

Read the notice with care. Look for these points:

If you did not get a notice but the drug store says your cost changed, call the plan. Ask the plan to send the notice and to state the change in full. Write down the date of your call and the name of the person who spoke with you.

Some changes are broad and hit all members who take a drug. Some are tied to a new plan year and come in fall mail. This guide is about changes during the year, not the fall letter for next year. Both kinds of mail matter, and both call for the same first step: read the full text, then check your own drugs one by one.

• The name and dose of the drug that will change.
• The kind of change, such as a new tier or a new rule.
• The date the change starts.
• What you can do if you need the drug as it is now.
• How to ask the plan for an exception or file an appeal.

How a change can hit your costs

Your drug costs for the year rest on a few base rules, plus your plan's own costs for each drug.

In 2026, the standard Part D deductible is at most $615 (Ledger A9). Your plan may set a lower deductible, or none at all for some tiers. Once you have met the deductible, you pay your share of each drug cost.

In 2026, once the drug costs you pay reach $2,100, you pay $0 for covered drugs for the rest of the year (Ledger A10). That cap helps if a tier move raises the cost of a drug you must take all year. It does not stop a mid-year change, but it does set a top limit on what you pay for covered drugs.

For 2027, the standard deductible will be $700 (Ledger A17) and the cap will be $2,400 (Ledger A18). Those sums are not yet in effect. They start with the 2027 plan year. Do not use them for your 2026 costs.

If drug costs strain your budget month to month, our guide on the Medicare Prescription Payment Plan shows how that plan lets you spread drug costs over the months of the year.

Who pays for what

• You pay the plan premium if your plan has one, plus your deductible and your share of drug costs, up to the cap for the year.
• Your plan pays its share of the cost for drugs on its list, under its tiers and rules.
• Medicare pays the plan under Part D rules and helps pay costs once you reach high drug costs for the year.
• Medicaid can help with drug costs for people who qualify through their state.
• Private pay covers drugs the plan does not cover, and costs you choose to pay on your own, such as a drug you buy with no plan claim.

Sample situation

Maria is 74 and takes one drug each day for her heart. In the spring, she gets a notice from her plan. The notice says her drug will move to a higher tier and will need plan approval first. Maria does not wait for her next refill. She calls the plan and asks what her new cost will be for that drug. The plan states its own cost for the drug, which is not the same as the tier name. She then calls her doctor. Her doctor says a like drug on the list could work, but the first drug has worked well for years. The doctor helps her ask the plan for an exception, with a note on why she needs that drug. The plan grants the exception. Maria keeps her drug, notes the new cost in her budget, and keeps the notice with her plan card. She also marks the fall window to shop and check the list for next year.

Your options if a change hurts you

You have more than one path. You can use one path, or more than one.

First, ask the plan for an exception. A coverage exception asks the plan to cover a drug it took off the list or to waive a new rule for you. A tier exception asks the plan to charge you the cost of a lower tier for a drug on a higher tier. Your doctor can help by stating why you need that drug or that tier. Ask the plan what form or note it needs, and keep a copy of all you send.

Second, ask your doctor about a like drug. If a drug on the list treats the same health need and costs less, your doctor may say it is a safe swap for you. Do not swap on your own. Some drugs that look alike are not a safe swap for a given person.

Third, file an appeal if the plan says no. An appeal asks the plan to look at its choice again. The notice and the plan denial letter tell you how to file. Follow those steps and keep proof of the date you sent your appeal. If the plan still says no, the denial letter tells you what next step you can take.

Fourth, shop at the next enrollment window. You can check the drug lists of other plans and pick one that covers your drugs at a cost that fits you. Use your full drug list, with doses, when you shop. A plan with a low premium can still cost more if your main drug sits on a high tier or has a new rule.

Steps to take this week

A mid-year change to your drug list is not the end of your choices. A notice gives you facts. An exception, a like drug, an appeal, and a new plan search each give you a way to act on those facts.

• Find your most recent notice and read it in full.
• List each drug you take, with the dose and how often you take it.
• Call the plan and ask for the true cost of each drug that changed.
• Call your doctor if a drug you need moved, gained a rule, or left the list.
• Ask about an exception, a like drug, or an appeal, based on your case.
• Keep all mail, forms, and call notes in one folder.

Sources

• https://www.medicare.gov/health-drug-plans/part-d/basics/costs