What is a Drug Formulary
A formulary is a list of prescription drugs covered by your health insurance plan, organized into tiers that determine how much you pay for each medication.
A formulary is the official list of prescription drugs that your health insurance plan covers. Also called a drug list, a formulary tells you which medications are covered, at what tier (which determines your cost), and any restrictions that apply — like needing prior authorization or step therapy before the insurer will pay for a drug.
Every health insurance plan has its own formulary, and they can differ dramatically. A drug covered at Tier 1 on one plan might be excluded or placed at Tier 4 on another. Checking the formulary for your specific medications is one of the most important steps when comparing health plans during open enrollment.
How Drug Tiers Work
Most formularies are organized into tiers, with lower tiers costing you less:
| Tier | Drug Type | Typical Cost |
|---|---|---|
| Tier 1 | Preferred generics | $0–$15 copay |
| Tier 2 | Non-preferred generics | $15–$40 copay |
| Tier 3 | Preferred brand-name | $40–$80 copay |
| Tier 4 | Non-preferred brand-name | $80–$150 copay |
| Tier 5 | Specialty drugs | Coinsurance (20–33%, often $200+) |
Some plans only have 3 tiers; others have 6. The exact copay or coinsurance varies by plan.
What "Non-Formulary" Means
If a drug is "non-formulary," it's not on the covered drug list at all. Your insurer won't pay for it under normal circumstances. You can:
- Ask your doctor about a therapeutically equivalent alternative that is on the formulary
- Request a formulary exception — your doctor submits medical documentation showing the non-formulary drug is medically necessary when formulary alternatives won't work
- Pay full price out-of-pocket (sometimes cheaper with discount programs like GoodRx)
Step Therapy and Prior Authorization on Formulary Drugs
Some formulary drugs come with conditions:
- Prior authorization: The insurer requires approval before covering the drug. Your doctor must document medical necessity.
- Step therapy: You must first try and fail on a lower-cost drug before the insurer will cover a higher-tier option. Controversial for patients with conditions requiring specific drugs.
- Quantity limits: The plan only covers a set amount (e.g., one month supply, specific number of pills) and requires additional approval for more.
Formulary Changes Mid-Year
Formularies can change during the plan year. If a drug you rely on is removed or moved to a higher tier, the insurer must generally provide 60 days' notice for non-specialty drugs. During open enrollment, check the formulary for the upcoming plan year — not the current year — to confirm your medications will still be covered at acceptable cost.
How to Check Your Plan's Formulary
- Visit your insurer's member website or plan's "Find Drugs" tool
- Search for each medication you take by name (brand and generic)
- Note the tier and any restrictions listed
- Calculate the estimated annual cost for each drug under each plan you're comparing
For expensive specialty medications, the formulary tier can be worth thousands of dollars per year — making it worth more scrutiny than even the deductible or premium comparisons.