What is a Medicare Part D formulary (drug guide)?

Medicare Part D helps cover the cost of prescription drugs and is offered to everyone who qualifies for Medicare. Each Part D plan has a list of drugs that are covered by the plan, called a Drug Formulary (or "Drug Guide").

Here are some details to explain what a Medicare Part D formulary is and how it works.

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.” Drug tiers are a way for insurance providers to determine medicine costs.

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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., shingles vaccine) except for vaccines covered by Part B.2

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 exceptions.

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 representative, your doctor or a non-physician prescriber. Explore these details on Medicare Part D Coverage Redetermination to learn more.

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 list of covered drugs for Medicare.

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.

Humana answers your Medicare questions


  1. “What Medicare Part D drug plans cover,” Medicare.gov, last accessed May 23, 2023, https://www.medicare.gov/drug-coverage-part-d/what-medicare-part-d-drug-plans-cover
  2. “Part D basics,” Medicare Interactive, last accessed May 23, 2023, https://www.medicareinteractive.org/get-answers/medicare-prescription-drug-coverage-part-d/medicare-part-d-coverage/part-d-basics.
  3. “Drugs excluded from Part D coverage,” Medicare Interactive, last accessed May 23, 2023, https://www.medicareinteractive.org/get-answers/medicare-prescription-drug-coverage-part-d/medicare-part-d-coverage/drugs-excluded-from-part-d-coverage.

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