Here are some details to explain what a Medicare Part D formulary is and how it works.
What is a Medicare Part D formulary (drug guide)?
4-minute readPublished 03/28/2024Updated 01:32 PM EST, 04/29/2025
What is a formulary?
In simple terms, a formulary is another name for a drug list. It’s an inventory of all the generic and brand-name prescription drugs covered by a Medicare drug plan. All Medicare drug plans generally must cover at least 2 drugs per drug category, but each individual plan can choose which drugs covered by Part D they will offer.1
What are formulary drug tiers?
Many plans arrange their list of covered drugs in different levels, called “tiers.”
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4-minute readPublished 03/28/2024Updated 01:32 PM EST, 04/29/2025
Medicare Part D prescription drug tiers
Medications covered by Medicare Part D are assigned to 1 of 5 tiers—from Tier 1 (generics) to Tier 5 (the highest cost drugs)—depending on their strength, type or purpose.
Your prescribed medications will be split into 3-Tier, 4-Tier or 5-Tier groupings according to your insurance plan.
If your plan features 3 tiers, Tier 1 includes generic drugs, such as low-cost preferred generics or general preferred generics. Tier 2 includes brand-name drugs, including preferred and non-preferred options. Tier 3 on a 3-Tier plan is for drugs with the highest costs.
If your part D coverage features 4 tiers, it includes Tiers 1, 2 and 3 and adds a 4th Tier for high-cost, mostly brand-name drugs.
If you have a 5-Tier plan, it will include Tiers 1 through 4 and adds a 5th Tier for the highest cost drugs, including most specialty medications used to treat rare, chronic, or complex health conditions.
What medications are covered under a Medicare Part D formulary?
In addition to at least 2 drugs per drug category, Part D drug plans must cover all drugs available in the following categories:2
- HIV/AIDS treatments
- Antidepressants
- Antipsychotic medications
- Anticonvulsive treatments for seizure disorders
- Immunosuppressant drugs
- Anticancer drugs (unless covered by Part B)
Note: Part D plans must also cover most vaccines (e.g.,
What medications are not covered under Medicare Part D formulary?
Outside of the mandatory drugs required by Medicare, each Part D drug plan can choose what it covers. Some of the drugs typically not covered include:3
- Drugs used to treat anorexia, weight loss or weight gain
- Fertility drugs
- Drugs used for cosmetic purposes or hair growth
- Drugs that are only for the relief of cold or cough symptoms
- Drugs used to treat erectile dysfunction
- Prescription vitamins and minerals (except prenatal vitamins and fluoride preparations)
- Non-prescription drugs/over-the-counter drugs
Note: Prescription drugs used for the above conditions may be covered if they’re prescribed to treat other conditions.3
What if my prescription is not on the formulary?
If your specific drug is not on the formulary, there are several actions you can take.
Use a similar drug on the formulary
In most cases, a similar drug to your specific drug should be available. If you or your prescriber believes none of the drugs on your plan’s formulary will work for your condition, you can request an exception.
Request a formulary exception
A formulary exception asks a provider to cover a drug not currently on its drug list. It may also ask a provider to waive a step therapy drug requirement or to waive quantity or dosage limits on a drug. For more information, check out this information on
File an appeal
If your exception is denied, you can file an appeal to ask the provider to reconsider their decision. Also called a redetermination, the appeal can be filed by you, your
Pay out of pocket
If you’re unable to win the appeal, you must pay 100% of the costs out-of-pocket for all drugs considered “non-formulary.” Paying for these uncovered medications does not count towards your plan deductible or annual out-of-pocket max.
How do I find if a Medicare Part D plan covers my prescription drugs?
The best way to see if your prescription drugs are covered is to check the plan’s formulary. If you’re a Humana member with a drug plan, you can simply explore our
Frequently asked questions
1. What’s the difference between formulary and non-formulary prescriptions?
Formulary prescriptions are included in a plan’s drug list and paid for by the plan. Non-formulary prescriptions are not included in the drug list and you pay 100% of the costs out of pocket. Non-formulary drugs can include over-the-counter medicines, experimental drugs or certain cosmetic or lifestyle medications.
2. Do all Medicare Part D plans have the same formulary?
No. All Part D plans generally must cover at least 2 drugs per drug category, but each individual plan can choose which drugs covered by Part D they will offer.
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4-minute readPublished 03/28/2024Updated 01:32 PM EST, 04/29/2025
Sources
- “
What do drug plans cover? ” Medicare.gov, last accessed Feb. 18, 2025. - “
Part D basics ,” Medicare Interactive, last accessed Feb. 18, 2025. - “
Drugs excluded from Part D coverage ,” Medicare Interactive, last accessed Feb. 18, 2025.