Part D formularies and drug tiers
Whether a drug is covered, and what it costs, depends on the plan's list.
Every Medicare drug plan has a formulary: its list of covered drugs. Formularies must include a range of drugs in each category, but each plan chooses the specific drugs, what tier they're on, and what rules apply to them.
Tiers
Most plans group drugs into tiers. Lower tiers, usually generics, cost less; higher tiers, such as specialty drugs, cost more. The same drug can be on a different tier, or not covered at all, in a different plan.
Coverage rules
- Prior authorization: your doctor must show the plan why you need the drug before it's covered.
- Step therapy: you must try a lower-cost drug that treats the same condition first.
- Quantity limits: a limit on how much you can get at a time.
Asking for an exception
You or your doctor can ask the plan to cover a drug that isn't on its formulary, to waive a coverage rule, or to cover a drug at a lower tier. Your doctor usually needs to provide a supporting statement. If the plan says no, you can appeal.
Transition fills
If you're new to a plan, or your plan's formulary changes, and you take a drug that isn't covered, the plan must generally give you a temporary supply in your first 90 days so you have time to switch drugs or request an exception.
Formularies change
Plans can change their formularies each year, and sometimes during the year. Your Annual Notice of Change lists next year's changes. Check your drugs every fall.
Common questions
Check the plan's formulary on its website, or enter your drugs in the Medicare Plan Finder, which shows coverage and estimated costs for every plan.
Plans can make some changes during the year, such as replacing a brand drug with a new generic. You'll generally be notified in advance.
Want help with your own choices?
Every state runs a State Health Insurance Assistance Program (SHIP) with trained counselors who give free, unbiased Medicare help and do not sell plans. Find yours on our Medicare by state pages, or call Medicare at 1-800-MEDICARE (1-800-633-4227) (TTY 1-877-486-2048, 24 hours a day, 7 days a week).
Planning the rest of your coverage in retirement? We can help with life insurance later in life and final expense coverage.
Sources
- Costs for Medicare drug coverage, Medicare.gov. Checked September 29, 2026.
- Joining a health or drug plan, Medicare.gov. Checked September 29, 2026.
General information about the federal Medicare program, not advice about your situation. Figures are for 2026 unless stated and change every year; last reviewed September 29, 2026. Quote My Policy is a private company. Not connected with or endorsed by the United States government or the federal Medicare program.
Quote My Policy does not sell Medicare plans on this site. For plan-specific help, contact Medicare at 1-800-MEDICARE (1-800-633-4227) (TTY 1-877-486-2048, 24 hours a day, 7 days a week) or your State Health Insurance Assistance Program.