Medicare Part D Formulary: Covered Drugs & Rules

What is a Medicare Part D formulary?

A formulary is the list of prescription drugs covered by a Medicare Part D plan. If a drug is on the formulary, the plan may help pay for it, subject to the plan’s deductible, copayment, coinsurance, pharmacy rules, and any coverage requirements.

Each Part D plan has its own formulary. This means a drug covered by one plan may not be covered by another plan, or it may be covered at a different cost level.

What drugs do Part D plans generally cover?

Medicare Part D generally helps cover outpatient prescription drugs that are not covered by Medicare Part B. Plan formularies can include:

Generic prescription drugs
Brand-name prescription drugs
Original biological products
Biosimilars
Many vaccines covered under Part D, including adult vaccines recommended by the Advisory Committee on Immunization Practices

Medicare says all Part D plans must cover a wide range of prescription drugs that people with Medicare take. Plans must also cover most drugs in certain protected classes, such as drugs used to treat cancer, HIV/AIDS, or depression.

Do all Part D plans cover the same drugs?

No. Part D plans must follow Medicare rules, but they do not all cover the exact same drugs. Each plan creates its own formulary, and formularies can vary by:

Which specific drugs are included
Whether the drug is generic, preferred brand, non-preferred brand, or specialty
Which tier the drug is placed on
Whether the plan requires prior authorization, step therapy, or quantity limits
Which pharmacies are in the plan’s network

Because formularies differ, people should check their own plan’s drug list rather than assuming a prescription is covered by all Part D plans.

How do drug tiers affect what you pay?

Many Part D formularies group covered drugs into cost levels called tiers. In general, drugs in lower tiers cost less than drugs in higher tiers, but the exact amount depends on the plan.

A drug being covered does not always mean it has the lowest out-of-pocket cost. The same medication may appear on different tiers in different plans. A plan may also use preferred pharmacies, which can affect what you pay for a covered prescription.

What coverage rules can apply to formulary drugs?

Some formulary drugs have coverage rules. Common examples include:

Prior authorization: The plan must approve coverage before it pays for the drug.
Step therapy: The plan may require you to try a lower-cost drug first, unless an exception is approved.
Quantity limits: The plan may limit how much of a drug it covers over a certain period.

These rules do not necessarily mean the drug is uncovered. They mean the plan may require additional steps before it pays for the prescription.

What if my drug is not on the formulary?

If your drug is not on your plan’s formulary, a similar covered drug may be available. You can ask your prescriber whether a formulary alternative may work for your condition.

If you or your prescriber believe none of the covered alternatives is appropriate, you can ask the plan for an exception. An exception may ask the plan to cover a drug that is not on the formulary or to waive a coverage rule. Approval is not automatic and depends on the plan’s review.

When coverage begins, some people may also qualify for a transition fill, which is a one-time temporary supply of a drug they have been taking that the plan does not cover or that requires prior authorization or step therapy.

How should you check whether your prescriptions are covered?

To check coverage, review the plan’s formulary before enrolling and again each year during plan review periods. Look up each prescription by exact drug name, dosage, and form. Also check the drug tier, any restrictions, and whether your preferred pharmacy is in the plan’s network.

Formularies may change during the year under Medicare rules, such as when new drugs become available, drug therapies change, or new medical information is released. If you take ongoing medications, reviewing your plan’s current drug list is an important part of comparing Part D coverage.

Our Process

From First Meeting to Medicare Enrollment

We begin by helping you understand how Medicare works and how the different pieces fit together. We walk through Original Medicare, Parts A and B, Medicare Advantage, Medicare Supplement insurance, and Part D prescription drug coverage, including how formularies, drug tiers, and plan rules can affect your costs.

We also explain dental, vision, and hearing coverage, along with other products that may help fill gaps in your healthcare plan. Depending on your needs, that may include short-term in-home healthcare coverage, hospital indemnity insurance, or coverage designed to provide additional financial support following a cancer diagnosis, heart attack, or stroke.

Once you understand the landscape, we move into the planning stage. That is when we review your doctors, hospitals, prescription drugs, current coverage, and other personal details so we can begin evaluating the Medicare plan options that fit your situation.

Discovery Meeting

We collect information about your doctors, hospitals, prescription drugs, current coverage, and other important details, then discuss your unique situation and priorities. Start your secure Medicare profile.

Create Your Strategy

We review the information gathered during discovery and develop a Medicare claiming and coverage strategy tailored to your circumstances.

Plan Enrollment

Once you are comfortable with the strategy, we help coordinate the appropriate enrollment steps and timing.

Annual Reviews

Medicare plans, costs, formularies, provider networks, and personal circumstances can change. We conduct annual reviews to help determine whether your current coverage still fits.

Request Medicare Planning Information

Official Sources

What do drug plans cover? | Medicare
Verifies that Part D plans must cover a wide range of prescription drugs and that each plan has its own formulary.
How do drug plans work? | Medicare
Explains formularies, covered drug types, exceptions, vaccines, and how plans may change drug lists.
Drug plan rules | Medicare
Verifies prior authorization, step therapy, quantity limits, exceptions, and transition fill rules.
Prescription drugs (outpatient)
Verifies that Part D covers many outpatient drugs not covered by Part B and that beneficiaries should check the plan formulary.
Formulary Guidance | CMS
Provides CMS information on Medicare prescription drug formulary policies and CMS review of Part D formularies.

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