The short answer
Your drug is covered if it is on your plan's list of covered drugs, called a formulary. Every plan has its own list, every list must hold at least two drugs in the most commonly prescribed classes, and a plan can change its list during the year.
You take the same drug you took last year. Same plan. Same pharmacy. And what you hand over at the counter is not the same. Nothing about you changed. Your plan added a generic version, moved your brand-name drug to a higher cost tier, and your share went up.
Is my drug covered by my Medicare plan?
Your drug is covered if it appears on your plan's formulary, the list of drugs that plan pays for. Each plan builds its own list. Medicare sets a floor of at least two drugs in the most commonly prescribed categories and classes, and the plan chooses which ones.
Read that floor again, because it is the honest answer to the question in the title. The rule guarantees that two drugs exist in your category. It does not guarantee that yours is one of them.
There is one place the rule is stronger. Every plan must include most drugs in certain protected classes. Those classes are:
- Cancer drugs
- HIV and AIDS drugs
- Antidepressants
- Antipsychotics
- Anticonvulsants
- Immunosuppressants for organ transplants
Outside those six, your plan picked its list from what was available, and a different plan picked a different one.
The coverage question has a date on it. This is our reading, not a rule Medicare states. Put three government facts side by side and you get a fourth thing.
The list has a floor of two drugs per class and the plan chooses the rest. The plan may change that list at any time. What you are told, and when, depends on why the change happened.
So "is my drug covered" is answered for a day, not for a year. The three facts are the government's. Treating the answer as dated is ours.
What is a formulary?
A formulary is a plan's list of covered drugs. Each plan has its own. The list can hold brand-name drugs, generic drugs, original biological products and biosimilars, and it is built to cover a wide range of the drugs people with Medicare take.
Two of those words are worth stopping on, because they decide what you pay later.
A generic drug is a copy of a brand-name drug. It matches the brand on dosage form, how it is taken, intended use, performance, quality, safety and strength, and its maker must prove to the Food and Drug Administration that it works the same way. Both brand and generic need that approval before anyone can prescribe them.
A biological product is a prescription drug made from natural and living sources such as animal cells, plant cells, bacteria or yeast. A biosimilar is a biological product that has to be highly similar to the original, with no clinically meaningful difference in safety or effectiveness. An interchangeable biosimilar can be swapped for the original at the pharmacy without a new prescription, subject to your state's laws.
That last sentence is the one people meet without noticing. Whether the substitution can happen at the counter without a new prescription depends on the laws of your state.
How do I check my drug?
You check your drug against your own plan's formulary, because there is no single Medicare list to check against. The plan publishes the list it actually uses. Medicare's plan finder at Medicare.gov/plan-compare shows which plans cover the drugs you take, which is the route to use before you join one.
Your Explanation of Benefits is the second place to look, and it is the one that shows what actually happened. Your plan sends it the month after the pharmacy bills them. It lists the prescriptions you filled, what the plan paid, what you and others paid, which coverage stage you are in, and what counted toward your out-of-pocket costs and your total drug costs.
A list tells you what is supposed to happen. The Explanation of Benefits tells you what did.
What if my drug is not covered?
If your drug is not on the list you pay full price for it, unless you qualify for an exception. Medicare's own wording is that in most cases a similar drug should be available. Plans negotiate lower prices for the drugs on their lists, so a drug on the list generally costs you less.
An exception is when a drug plan decides to cover a drug that is not on its list, or to waive a coverage rule. You or your prescriber has to request it, and your doctor or other prescriber has to give a supporting statement explaining the medical reason.
That supporting statement is the whole hinge. The request is not a form you win by filling in correctly. It is a clinical argument your prescriber makes, and it comes from them.
Plans can also attach rules to a drug that is on the list. Prior authorization, step therapy and quantity limits are the three you will see named, along with medication safety checks. They are covered in this publication's article on Part D access restrictions, which is where the process for each one belongs.
Can the plan change the list mid-year?
Yes, and this is the part most people never hear about until it reaches the counter. A plan can change its drug list during the year under guidelines Medicare sets. It may do so when drug therapies change, when new drugs are released, or when new medical information arrives.
Whether you are warned depends entirely on why the list changed.
Here is the difference, in the government's own terms.
| Why the list changed | Warned in advance | What you get |
|---|---|---|
| The FDA finds a drug unsafe, or the maker pulls it | No | Your plan tells you after the drug has been removed |
| The plan adds a new generic and drops or reprices the brand | No | Your plan tells you after the replacement |
| Any other change to a drug you take | Yes | Written notice at least 30 days before it takes effect |
| Any other change, told at the counter instead | At refill | Written notice plus at least a month's supply under the old rules |
The bottom two rows are the same rule. It gives your plan two ways to satisfy it. Either you get 30 days of warning, or you get a month's supply on the old terms while you work out what to do.
The top two rows have no warning in them at all, and for a safety removal that is the point.
Your cost can move without the list moving too. Coinsurance can rise for a drug when the manufacturer raises the price. It can also rise when the plan adds a generic or biosimilar, moves your brand-name drug to a higher cost-sharing tier, and you keep taking the brand.
Nothing in that sentence requires anything of you. That is what makes it worth knowing.
What are my options?
You have three routes when the list does not give you what you need, and they are different in kind. You can switch to a covered drug, ask for an exception, or move to a different plan. Only the first two are things you can do today.
Switching is the route Medicare describes first, because in most cases a similar drug is on the list. It is a conversation with your prescriber, not with your plan.
The exception route is the one that keeps your drug. Your prescriber supplies the medical reason. There is also a narrower version for price rather than coverage: a tiering exception, where the plan agrees to charge you the lower amount for a drug sitting on its non-preferred tier.
Moving to a different plan is the third route, and it runs on a calendar rather than on a clinical argument. This publication's articles on the enrollment windows carry the dates.
Medicare.gov adds one observation of its own here, and it is theirs rather than ours: if you take a lot of generic prescriptions, it suggests looking at plans whose tiers charge no copayment, or a low one, for generics.
What this means for you
Your drug is covered if it is on your plan's list. The list has a floor of two drugs in the most commonly prescribed classes, a stronger rule for six protected classes, and beyond that it is your plan's own choice.
The list is not fixed. A plan can change it at any time, and what you are owed depends on why. A safety removal reaches you after the fact. Any other change to a drug you take comes with 30 days of written notice, or a month's supply on the old terms at your next refill.
Your price can also move on its own, when a manufacturer raises a price or when a new generic pushes your brand-name drug up a tier.
So check the list, and then check the mail. The letter that changes your costs looks like every other envelope your plan sends.
For what the tiers mean and what each one costs, read this publication's article on Part D drug tiers. For prior authorization, step therapy and how an exception is actually filed, read the articles on Part D access restrictions.
FAQ
Does every Medicare drug plan cover the same drugs?
No. Each plan has its own formulary, which is its list of covered drugs, and each plan chooses what goes on it. Medicare sets a floor rather than a list: every plan's formulary must include at least two drugs in the most commonly prescribed categories and classes.
Above that floor the plan decides. There is one stronger rule. Every plan must include most drugs in six protected classes, which are cancer drugs, HIV and AIDS drugs, antidepressants, antipsychotics, anticonvulsants, and immunosuppressants for organ transplants.
This is why two people on the same medication can get different answers from different plans, and why the only list that answers your question is the one belonging to the plan you actually hold.
What happens if I fill a prescription for a drug that is not on my plan's list?
You pay full price for it, unless you qualify for an exception. Medicare states this plainly, and it also states the reason a covered drug costs less: all Medicare drug plans have negotiated lower prices for the drugs on their own lists.
A drug off the list has no negotiated price behind it, so what you pay is the price itself rather than a share of it. Medicare's guidance is that in most cases a similar drug should be available on your plan's list.
If you or your prescriber believe none of the drugs on the list will work for your condition, the exception route exists, and your prescriber has to supply a statement giving the medical reason.
How much notice does my plan have to give before it changes its drug list?
It depends on why the list is changing, and the difference is large. If the Food and Drug Administration considers a drug unsafe, or the manufacturer removes it from the market, plans may remove it immediately, and you are notified after it is gone.
The same after-the-fact notice applies when a plan meeting certain requirements replaces a brand-name drug with a new generic. For any other change involving a drug you are currently taking, your plan must do one of two things.
It must give you written notice at least 30 days before the change takes effect, or, at the time you request a refill, give you written notice plus at least a month's supply under the same rules as before.
Why did my copayment go up when I did not change anything?
Two causes are named by Medicare and neither one involves you. Your coinsurance, the percentage you pay for a drug at the pharmacy, can rise for a particular drug when the manufacturer raises its price.
Your copayment or coinsurance can also rise if you keep taking a brand-name drug or original biological product after your plan adds a generic or biosimilar version to its list and moves the brand-name drug to a higher cost-sharing tier.
In the second case the drug is still covered. It has simply moved to a more expensive shelf, and staying on the brand is what carries the higher price. Your Explanation of Benefits will show which stage and which amounts applied.
What is an exception, and who asks for it?
An exception is when a drug plan decides to cover a drug that is not on its drug list, or to waive one of its coverage rules.
There is also a narrower form called a tiering exception, where the plan agrees to charge a lower amount for a drug that sits on its non-preferred tier. Either you or your prescriber must request it. Your doctor or other prescriber must then provide a supporting statement explaining the medical reason for it.
That statement is the substance of the request. The process for filing one, how long a decision takes, and what happens if it is denied are covered in this publication's articles on Part D access restrictions.
Can my pharmacy swap my biological drug for a different version?
An interchangeable biosimilar may be substituted for the original biological product at the pharmacy without a new prescription, subject to your state's laws. A biological product is a prescription drug made from natural and living sources such as animal cells, plant cells, bacteria or yeast.
A biosimilar has to be highly similar to the original, with no clinically meaningful differences in safety or effectiveness. The word interchangeable is doing specific work in that sentence: not every biosimilar carries it.
Because the substitution rule depends on where you live, the answer for your prescription is a question for your pharmacist, and your plan's list still decides what the plan pays toward whichever version you leave with.
