What is a Part D Formulary?
A formulary is a list of prescription drugs that a Medicare Part D plan covers. Each plan has its own formulary, which is organized into tiers. Drugs on lower tiers generally have lower cost-sharing (copays or coinsurance) than drugs on higher tiers. Plans must cover at least two drugs in each therapeutic category and class, and all drugs in six 'protected classes' (antidepressants, antipsychotics, anticonvulsants, immunosuppressants, antiretrovirals, and antineoplastics).
Drug Tier Structure
Most Part D plans use a 5-tier formulary:
| Tier | Drug Type | Typical Cost |
|---|---|---|
| Tier 1 | Preferred Generic | $0 – $15 copay |
| Tier 2 | Generic | $5 – $25 copay |
| Tier 3 | Preferred Brand | $25 – $60 copay |
| Tier 4 | Non-Preferred Brand | $60 – $150 copay |
| Tier 5 | Specialty | 25%–33% coinsurance |
How to Check if Your Drug is Covered
Before enrolling in a Part D plan, always verify your medications are on the formulary:
- Use Medicare.gov Plan Finder - enter your drugs to see which plans cover them and at what cost
- Visit the plan's website and search the formulary directly
- Call the plan's member services number
- Work with a licensed Medicare agent who can check multiple plans at once
Formularies change every January 1. Even if your drug was covered last year, check again during Annual Enrollment Period to make sure it's still covered at the same tier.
What to Do If Your Drug Isn't on the Formulary
If your medication isn't covered or is on a high-cost tier, you have options:
- Request a formulary exception - ask the plan to cover your drug at a lower cost-sharing level if your doctor certifies it's medically necessary
- Ask about therapeutic alternatives - your doctor may be able to prescribe a covered drug in the same class
- File an appeal if your exception request is denied
- Switch plans during Annual Enrollment Period to one that covers your drug