Part D Formulary Changes: How to Check Your Drugs Before Open Enrollment Ends

What a Formulary Is, and Why It Moves

A formulary is a plan’s list of covered drugs. Every Part D plan, whether it is a standalone drug plan or part of a Medicare Advantage plan, has one. The list is organized into tiers, and each tier carries a different cost. In general, lower tiers hold lower-cost generic drugs, higher tiers hold brand-name and specialty drugs, and the higher the tier, the more you pay at the pharmacy.

Plans revise their formularies for several reasons. A new generic becomes available. A manufacturer’s price changes. The plan negotiates a different arrangement with a drug company. New safety information appears. And because plans carry a larger share of the cost of expensive drugs under the redesigned Part D benefit, they can have added reasons to manage high-cost drugs more tightly. The result is that the list you saw last year is not necessarily the list you will get.

Your plan’s Annual Notice of Change is where it tells you about the major differences. Our guide to reading your Annual Notice of Change shows where to look in that document. But the notice summarizes. For a medication-by-medication answer, you need to check the formulary itself.

Three Ways a Drug Can Change

Change	What it means for you	What you can do
Removal	The plan no longer covers the drug	Ask your prescriber about a covered alternative or an exception
Higher tier	Still covered, but costs more	Ask for a tiering exception
New restriction	Prior authorization, step therapy, or quantity limit	Your prescriber can request approval or an exception

When people say a drug is “no longer covered,” they usually mean one of three different things. Each calls for a different response.

The first is removal. The drug is dropped from the formulary. Unless an exception applies, the plan will not pay for it.

The second is a move to a higher tier. The drug is still covered, but your share of the cost increases. This is common and easy to miss, because the drug does not disappear, it just gets more expensive.

The third is a new restriction, which is what the industry calls utilization management. There are three main types:

• Prior authorization. Your doctor has to get the plan’s approval before it will pay for the drug.
• Step therapy. You must try one or more lower-cost drugs first, and the plan pays for the one you want only if those do not work.
• Quantity limits. The plan caps how much it will cover per fill or per month.

A drug can be on the formulary, at a tier you can afford, and still be difficult to get because of one of these restrictions. That is why a check needs to cover all three, not just whether the drug appears on the list.

How to Check Each Drug

Gather your medication list before you start. For each drug, write the exact name, the strength, the form such as tablet or injection, and how much you take. These details matter, because a plan can cover one strength or form differently from another.

Then use three sources, in this order.

• Medicare Plan Finder at Medicare.gov. Enter each drug, choose your pharmacy, and the tool shows which plans cover it, what tier it is on, whether restrictions apply, and your estimated cost. This is the fastest way to compare many plans at once.
• The plan’s own formulary. Plans publish a searchable formulary on their websites and must make the full list available. Check the specific plan, not just the insurer, because one company often sells several plans with different drug lists.
• A call to the plan. For anything important or unclear, call member services and ask them to confirm the tier, restrictions, and estimated cost for the coming year. Write down the date and the name of the person you spoke with.

Take special care with medications that are costly, that you take for a serious condition, or that have no good substitute. For those, ask your prescriber whether a covered alternative would be acceptable, and do not change or stop any medication on your own because of a formulary change. That decision belongs to you and your prescriber.

You can also check what the plan considers a covered drug at all. Part D covers prescription drugs for medical purposes, but certain categories have long been excluded by law, and weight-loss drugs are the best-known example. Rules in this area have been evolving: a temporary federal program that began in mid-2026 gives some eligible people access to certain weight-loss drugs outside their plan’s regular drug benefit. See our post on Wegovy, Zepbound, and similar drugs for how it works. For any drug in a category like this, confirm coverage with the plan directly instead of assuming.

Do Not Forget the Pharmacy

The pharmacy you use affects your cost. Many plans have preferred pharmacies, which charge less, and standard pharmacies, which charge more. Some also have mail-order options for maintenance drugs. A drug that looks affordable at one pharmacy can cost noticeably more at another, so enter your actual pharmacy in Plan Finder and compare a couple of alternatives. If your pharmacy changes status from one year to the next, that shows up in your costs even though the formulary is unchanged.

How This Looks for Each Kind of Coverage

Where your drug coverage comes from changes what you can do during the fall window.

Your coverage	Drug list you check	What to know
Original Medicare with a standalone Part D plan	The standalone plan’s formulary	You can switch drug plans without touching your doctors
Medicare Advantage with drug coverage	The Advantage plan’s formulary	Drug and medical coverage are one package, so a change affects both
Employer or retiree drug coverage	The employer’s drug list	Check that it counts as creditable before dropping or changing anything
VA or TRICARE drug coverage	That program’s rules	Generally counts as creditable, but confirm for your own coverage

If you have Original Medicare and a separate Part D plan, the check in this post is the whole job. You can pick a different drug plan during the window without changing which doctors you see. If you are in a Medicare Advantage plan that includes drug coverage, the drug benefit and medical benefit come as one package, so a better drug list may come with a different network or different copays. In that case, review both together. If you are in a Medicare Advantage HMO or PPO that includes drug coverage, you generally cannot add a separate drug plan. According to Medicare.gov, joining a stand-alone drug plan will disenroll you from that Advantage plan and return you to Original Medicare. Ask before you sign up for anything.

If you have drug coverage through a former employer, a union, the VA, or TRICARE, the question is not only whether the drugs are covered but whether the coverage counts as creditable, meaning it is expected to pay at least as much as standard Part D. Medicare.gov lists employer or union coverage, VA coverage, and TRICARE among the sources that may be creditable, and your current plan must tell you each year whether its coverage is. Employers and unions that offer drug coverage generally send that notice each fall. If you drop creditable coverage, or if your coverage is not creditable and you skip Part D, you may face a late enrollment penalty if you go 63 days or more without creditable drug coverage after you were first eligible. Check before you cancel anything, and get the creditable-coverage notice in writing. We are an independent agency, not affiliated with the VA, TRICARE, or the Department of Defense, so confirm details with them directly.

What Changes During the Year

The formulary you see in the fall is not frozen. Federal rules allow plans to make some changes during the plan year, with protections for people already taking an affected drug.

In general, when a plan removes a drug, adds a new restriction such as prior authorization or step therapy, or moves a drug to a higher tier, federal Part D rules require it to notify affected members. The plan can give written notice at least 30 days before the change takes effect, or, when an affected member requests a refill, it can provide an approved month’s supply of the drug along with written notice of the change. Replacing a brand-name drug with a new generic or a biosimilar, and removing a drug withdrawn from the market, can be handled differently: plans may do these immediately, after giving members a general advance notice that such changes can happen, and then send notice to affected members shortly afterward. The details vary by type of change, so if your plan tells you about a mid-year change, read the notice carefully and call the plan with questions.

The practical point is that a mid-year change should not leave you at the pharmacy counter with no warning and no supply. But it can still raise your cost or require you to change drugs. If that matters, talk to your prescriber early.

Transition Fills: A Safety Net When You Switch Plans

If you join a new Part D plan and a drug you take is not on its formulary or has a restriction that would block it, plans are required to have a transition process. As the CMS manual and federal rules describe it, plans must provide a temporary supply of the drug, at least a month’s supply unless your prescription is written for less, during the first 90 days of your coverage under the plan. A temporary supply is intended to give you and your prescriber time to find a covered alternative or request an exception. If you enroll effective November 1 or December 1, the transition period carries into the new year, and in some cases current members affected by a formulary change from one year to the next are covered by a transition process too. Ask your plan how it applies.

Transition fills are a bridge, not a plan. Use the time to act: ask your prescriber about a formulary alternative, or ask for a formulary exception, which is described below. Do not treat the temporary supply as a sign that the drug will be covered later.

If a Drug You Need Is Not Covered: Exceptions

You are not stuck with a “no.” Part D has a process called a coverage determination, and within it you can ask for an exception. There are two common types.

A formulary exception asks the plan to cover a drug that is not on its list, or to waive a restriction such as step therapy or a quantity limit. A tiering exception asks the plan to charge you the cost of a lower tier for a drug that sits on a higher one. Plans are allowed to exclude drugs on a specialty tier from tiering exceptions, so ask whether that applies to your drug.

To request one, you or your prescriber contacts the plan. Your prescriber must supply a supporting statement explaining why the drug is medically necessary, for example that the preferred alternatives were tried and did not work or would be harmful. According to CMS guidance, the plan must give its decision within 72 hours of receiving the prescriber’s statement for a standard request, and within 24 hours for an expedited request, when your health could be seriously harmed by waiting.

If the plan says no, you have the right to appeal. The denial notice lists your deadline and your next step. An approved exception generally stays in effect through the end of the plan year as long as your prescriber keeps prescribing the drug and it remains safe for you, so it pays to make the request early. Whether it continues into the next plan year is up to the plan.

What the Part D Cap Means for This Check

Part D also has an annual limit on what you pay out of pocket for covered drugs, which is adjusted over time. Once you reach it, you generally pay nothing more for covered drugs for the rest of the year. That cap makes the formulary check even more important in one way: the cap only applies to covered drugs. A drug the plan does not cover does not count toward it. Medicare.gov lists the cap for the coming year and the maximum deductible a plan may charge. You can also ask about the Medicare Prescription Payment Plan, which lets you spread your out-of-pocket drug costs across the year instead of paying them all at the pharmacy counter. Our overview of Medicare Part D explains how the benefit phases work.

A Short Checklist for the Weeks Before December 7

• Make a list of every drug, with strength, form, and quantity.
• Check each one in Plan Finder for your current plan and for alternatives.
• Note any tier increase, prior authorization, step therapy, or quantity limit.
• Confirm your pharmacy and any alternatives.
• For any costly or hard-to-replace drug, talk to your prescriber about options.
• Make your decision and enroll before December 7. The plan has to receive your request by then.

If you also want the bigger picture, see our plan comparison checklist and our overview of the Annual Enrollment Period. Vaccines are a separate topic, since many recommended vaccines are covered under Part D with no cost-sharing, as described in our post on shingles, flu, and RSV vaccines.

Costly Mistakes to Avoid

• Checking only the drug name. The strength, form, and quantity can change coverage and cost. Check exactly what is on your prescription.
• Looking only at tier. A drug can sit on a reasonable tier and still require prior authorization or step therapy.
• Forgetting the pharmacy. The same drug can cost different amounts at different pharmacies in the same plan.
• Assuming your new plan will cover what your old one did. Plans differ, and a transition supply is a bridge, not a guarantee.
• Waiting until you are at the counter. A rejected claim on January 2 leaves you with fewer options than a check in November.
• Paying cash without asking. Money you pay outside your plan may not count toward your out-of-pocket total, so ask the plan how it treats such purchases before you assume.
• Changing or stopping a drug on your own. Always make that decision with your prescriber.

Three Pictures of How This Can Play Out

These are hypothetical scenarios meant to show the reasoning, not real cases.

Picture a retiree whose annual notice says that one of his medications is moving to a higher tier. He enters his drug list in Plan Finder and sees that another plan puts the same drug on a lower tier and covers his other medications too. The premium is a bit higher. He compares the yearly totals Plan Finder estimates, decides the other plan is the better fit, and enrolls well before December 7.

Picture a woman who takes a specialty drug that her plan covers only with prior authorization. Her notice does not mention a change, but she checks the formulary and finds a new quantity limit. She asks her prescriber’s office whether the limit fits her dose. The office tells her they can request an exception, and she decides to ask her plan about it in November rather than in January, so there is time for an answer.

Picture a man who finds, at the pharmacy in the first week of the year, that his new plan will not cover his medication without approval. The pharmacist tells him the reason for the rejection. He calls his plan, asks about a temporary supply, and asks his prescriber to start the approval request the same day. He gets a temporary fill and the request moves forward while he has medication in hand.

What to Gather and What to Ask

Before you call a plan or an agent, gather your medication list with names, strengths, forms, and quantities, your pharmacy information, and last year’s plan notice. When you ask, useful questions include:

• Is each of my drugs on the formulary for next year, and at which tier?
• Do any of them need prior authorization, step therapy, or a quantity limit?
• What will I pay for each at my pharmacy, and at a mail-order pharmacy?
• If a drug is not covered, how do I request an exception and how long does it take?
• What happens if I need a drug that is newly approved or not on the list?
• Does the plan offer a way to spread out my costs across the year?

If a Claim Is Rejected at the Pharmacy

A rejected claim feels like a dead end, but it usually has a specific cause. Work through it in order.

• Ask the pharmacist why the claim was rejected. Common reasons include the drug not being covered, needing prior authorization, step therapy, a quantity limit, or the wrong plan information on file.
• If the plan information is wrong, give the pharmacy your current card. A new card may not yet be in their system.
• Call the plan’s member services, using the number on your card. Ask about a temporary or emergency supply, and ask what the plan needs from your prescriber.
• Call your prescriber’s office. Ask them to submit the prior authorization or exception request, with the supporting statement. Ask for an expedited review if waiting could harm your health.
• Ask whether a covered alternative would work for you. That is a decision for you and your prescriber.
• If the request is denied, read the notice for your appeal deadline and the next step, and keep a log of your calls.
• If cost is the barrier, ask about Extra Help, which assists people with limited income and resources, and about the Medicare Prescription Payment Plan, which spreads out costs without reducing the total.

If you cannot get a needed medication, do not simply go without. Tell your prescriber right away so they can help you find an option.

Frequently Asked Questions

Can my Part D plan remove a drug during the year?

Plans can make some formulary changes during the year, but they generally must either give affected members at least 30 days’ notice or, when you request a refill, provide a month’s supply of the drug along with notice. Some changes, such as swapping in a generic, can be made with notice afterward. Check your plan’s notice for the specific terms.

What is a tiering exception?

It is a request that the plan charge you the cost-sharing of a lower tier for a drug that sits on a higher one. Your prescriber has to explain why the lower-tier alternatives are not suitable.

What is a transition fill?

It is a temporary supply, generally at least a month’s worth, that a plan provides during your first 90 days in the plan when a drug you take is not covered or is restricted. It gives you time to switch drugs or request an exception.

How quickly must a plan answer an exception request?

According to CMS guidance, within 72 hours of receiving the prescriber’s supporting statement for a standard request, and within 24 hours for an expedited request.

Where do I check whether my drug is covered?

Use the Medicare Plan Finder with your exact drug, dose, and pharmacy, then confirm with the plan’s own formulary and, for anything important, a call to the plan.