Each Medicare Part D plan maintains a formulary — the complete list of prescription medications the plan will cover. Because formularies directly influence your out-of-pocket drug costs, they are among the most critical factors to consider when selecting a Part D plan.
What Exactly Is a Formulary?
A formulary is a catalog of medications arranged by therapeutic category and cost tier. Each plan's pharmacy and therapeutics committee — a panel of physicians and pharmacists — creates the formulary by evaluating drugs for safety, efficacy, and cost.
Medicare mandates that every Part D formulary include drugs spanning all therapeutic categories and classes, guaranteeing beneficiaries can access treatments for every major health condition. Still, the exact drugs included and where they fall on the tier system can vary widely from one plan to another.
Understanding the Tier Structure
The majority of Part D formularies follow a five-tier framework:
Tier 1: Preferred Generic
- The lowest-cost generic medications
- Generally the most budget-friendly choice, with copays frequently below $15
- Examples: metformin, lisinopril, atorvastatin
Tier 2: Generic
- Additional generic drugs not included on the preferred list
- Cost-sharing is somewhat higher than Tier 1
- Still significantly cheaper than brand-name options
Tier 3: Preferred Brand
- Brand-name medications for which the plan has secured favorable pricing
- Copays tend to fall in the $30-$50 range
Tier 4: Non-Preferred Brand
- Brand-name drugs that are not on the preferred list
- Higher coinsurance applies, usually 30%-40% of the drug price
Tier 5: Specialty
- Expensive medications for treating complex or uncommon conditions
- Coinsurance is typically 25%-33% of the drug price
- Frequently subject to quantity restrictions and prior authorization
Utilization Management Restrictions
Plans may use certain management tools on specific medications:
- Prior authorization: The plan must give approval before the drug will be covered
- Step therapy: You are required to try a less expensive drug first before the plan covers the costlier alternative
- Quantity limits: Caps on how much of a medication you can obtain within a given time period
When the Formulary Changes
Plans have the ability to modify their formularies throughout the year, but Medicare requires them to:
- Give affected members no fewer than 60 days of advance notice
- Supply a transition fill for new enrollees who are currently taking a medication being dropped
- Permit members to file a formulary exception request
Checking What Your Plan Covers
- Go to Medicare.gov and use the Plan Finder tool to look up plans that include your specific prescriptions
- Visit the plan's website to review its most up-to-date formulary
- Phone the plan directly to verify coverage details and any restrictions on your medications
- Consult your pharmacist, who can often access formulary information through their system
Filing a Formulary Exception
If your medication is excluded from the formulary or placed on a tier you believe is too high, you have the right to request an exception. Your physician will need to submit a statement explaining why that particular drug is medically necessary for you. The plan is required to respond to standard requests within 72 hours and urgent requests within 24 hours. If your exception is denied, you have the right to appeal the decision.
Picking a plan whose formulary lists your medications on favorable tiers is one of the best ways to keep your prescription drug costs under control.