What Your Plan Can and Cannot Change About Your Drug List Mid-Year

A letter arrives saying your plan is changing its drug list. Or worse, no letter arrives and you find out at the pharmacy counter, holding a prescription you have filled for six years, being told it will now cost four hundred dollars.

Plans are allowed to change their drug lists during the year. They are not allowed to do it however they like. The rules are more protective than most people know, and the protections are almost never used because nobody explains them.

Here is what a plan can and cannot do to you mid-year.

The general rule, and the exception that protects you

Before a plan makes a negative change to its formulary, it generally has to submit that change to Medicare first. Two kinds of change are treated very differently.

Maintenance changes are the routine ones, and they are deemed approved 30 days after the plan submits them unless Medicare says otherwise.

Non-maintenance changes require the plan to wait for actual approval from Medicare. And here is the sentence worth reading twice, because it is the strongest protection in the whole system:

Affected enrollees are exempt from non-maintenance changes for the remainder of the contract year.

If you are already taking the drug and the plan makes a non-maintenance change to it, you are exempt for the rest of the year. You keep your coverage on the old terms until January. That is in the regulation, not a courtesy.

When a plan can move immediately

Two situations let a plan act without waiting.

Safety and market withdrawal. A plan may immediately remove any drug that the manufacturer has withdrawn from sale, or that the Food and Drug Administration determines was withdrawn for safety or effectiveness reasons. This one you want them to be able to do quickly.

Generic or biosimilar substitution. A plan may substitute immediately when it adds the corresponding generic or biosimilar at the same or a lower tier with the same or less restrictive rules, where that product was not available when the formulary was submitted, and where advance notice was given.

Note what the second one actually requires. Same or lower tier. Same or less restrictive rules. A plan cannot use "we added the generic" as cover for putting you on something with a prior authorization requirement that your brand did not have.

The blackout window

There is a period when a plan may not make negative changes at all, other than the immediate safety and substitution changes above: from the start of the annual election period through 60 days after the contract year begins.

That matters practically. It means the drug list you were shown while you were choosing a plan in the fall cannot be quietly worsened while you are choosing, or in January and most of February after you have committed. If you compare plans in October, the comparison is protected for a while.

The notice you are owed

A plan must give notice of a formulary change at least 30 days before the change takes effect, to Medicare and to specified entities. For you as an enrollee, the requirement is written notice either 30 days in advance or provided with your refill.

Medicare's consumer-facing summary is shorter than the regulation: plans can change their drug list during the year, and your plan must notify you of any changes that affect drugs you are taking. The limits described above, the blackout window and the exemption for affected enrollees, are in the regulation rather than in that summary.

"Provided with your refill" is the loophole that generates most of the unpleasant surprises. Read the paper that comes stapled to the bag. That is frequently where the notice is.

If you are new to a plan: the transition fill

This is the protection that keeps people from going without in January, and a great many people do not know it exists.

When you start on a new plan and a drug you have been taking is not on the formulary, or carries prior authorization or step therapy you have not been through, the plan must give you a temporary supply. The regulation says at least an approved month's supply, and the transition period covers your first 90 days of coverage under the new plan. Medicare's consumer page describes it as a one-time 30-day supply, which is the floor rather than the whole rule.

The plan then has to send you written notice within three business days after that temporary fill is processed. If you receive Extra Help, the plan cannot charge you more than the statutory copay maximums for a transition supply.

Use that month. It exists so you have time to either get an exception approved or work out an alternative with your prescriber, not so you can be surprised twice.

How to actually fight a change

You have a real process here, with real deadlines. Use it.

Who can ask. You must request a standard coverage determination from your plan. For an exception specifically, either you or your prescribing physician or other prescriber may file the request.

What your prescriber has to say. The supporting statement has to state that the plan's preferred drug or drugs either would not be as effective for you, or would have adverse effects for you, or both. That is the actual legal standard, and it is worth telling your doctor's office in those words, because a note saying "patient prefers this one" does not meet it.

Two kinds of exception. A tiering exception asks the plan to treat a non-preferred drug at a better cost-sharing level; the plan must grant it whenever it determines the requested drug is medically necessary. A formulary exception asks the plan to cover an off-formulary drug; the plan must grant it whenever it determines the drug is medically necessary and would be covered except for the fact that it is off the formulary.

The clocks.

• Standard coverage determination: within 72 hours. For an exception, the 72 hours runs from receipt of your prescriber's supporting statement. If no statement ever arrives, the plan has 72 hours from the end of 14 calendar days after your request.
• Expedited coverage determination: within 24 hours.
• Standard request for payment of a bill you already paid: within 14 calendar days.
• First-level appeal, a redetermination, on a standard benefit request: within 7 calendar days. On a payment request: 14 calendar days. Expedited: within 72 hours, with oral notice confirmed in writing within 3 calendar days.

Above the plan there are four more levels: an independent review entity, an administrative law judge at the Office of Medicare Hearings and Appeals, the Medicare Appeals Council, and federal district court.

And once you win, you should not have to win again. After an exception is approved, the plan may not require you to request approval for a refill or a new prescription, as long as your prescriber keeps prescribing the drug, it remains safe for you, and your enrollment period has not expired.

What to do the day the letter arrives

1. Read the whole notice, including the paper stapled to your prescription bag. Find out whether the change is a removal, a tier move, or a new restriction, and the effective date.
2. Check whether you are exempt. If it is a non-maintenance change and you were already taking the drug, you may be protected for the rest of the year. Ask the plan directly: "Is this a maintenance or a non-maintenance change, and am I an affected enrollee exempt for the remainder of the contract year?" That question, asked in those words, gets a different quality of answer than "can you help me."
3. Call your prescriber's office and tell them what the plan needs. Not effective for me, or adverse effects, or both. Give them the standard.
4. Ask for expedited review if waiting could seriously jeopardize your life, your health, or your ability to regain maximum function. That is the actual standard, and meeting it gets you 24 hours instead of 72.
5. If you are told to pay cash while you sort it out, keep every receipt and submit them for reimbursement. And know that if you buy the drug on a discount card instead of through your plan, what you spend does not count toward your annual out-of-pocket ceiling, which is $2,100 in 2026.
6. Put it on the list for the fall. A drug that got harder this year is a reason to compare plans in October rather than letting the renewal happen to you.

The part that gets skipped

A formulary change is not only an insurance problem. It is a clinical one.

If a plan pushes you to a different drug in the same class, that substitution may be entirely fine, or it may interact differently with something else you take, or come in a different strength that changes how you dose it, or be a device you have never used. A pharmacist who has your whole list can see interactions that a prescriber treating one condition may not have in front of them, and the plan is not looking at that question at all.

Take the letter to your pharmacy. Ask what the proposed alternative would mean alongside everything else you take. That is free and it is the step people skip.

Why we wrote this

Haven Health was started by the pharmacists at Good Day Pharmacy, here in Northern Colorado. Before we were licensed, our part in this was reading these letters out loud in February, with no way to change the plan they described. That is the part that changed.

This describes Medicare's rules, not any particular plan's benefits. Dollar figures are 2026 figures and change each January.

Write down the date the notice arrived, who you spoke to, and what they said. That record is what an appeal runs on, and it is the difference between believing you were treated unfairly and being able to show it.

If a letter came and you do not know what it means, bring it. Bring the medication list too. We will read both like pharmacists. And you will hear from us in February, not only in October, because February is when these letters actually arrive.