Formulary
Updated for plan year 2026
In plain terms
A formulary is the list of prescription drugs a health plan covers, usually organized into tiers that determine your cost. Lower tiers hold generics with small copays; higher tiers hold brand-name and specialty drugs with larger copays or coinsurance. Plans update their formularies and may require steps like prior authorization or trying a cheaper drug first. Two plans with similar premiums can treat the same medication very differently, so the formulary is where you check whether your prescriptions are covered and at what cost.
A plain example
You take a brand-name maintenance drug. On one plan it sits on a low tier with a $40 copay; on another it's a high specialty tier charging 30 percent coinsurance, which on a $500 drug is $150 a month. Same medication, same premiums, but a $1,320 difference over a year that only the formulary reveals.
Why it matters
If you take regular medication, the formulary can matter more than the premium. A plan that looks cheap can bury your drug on a high tier or leave it off entirely, so checking each prescription against the formulary is the surest way to avoid a costly surprise at the pharmacy.
A common point of confusion
A drug being covered doesn't mean it's cheap. Its formulary tier sets your cost, and a covered brand-name drug on a high tier can cost far more than a generic, sometimes more than paying cash. Formularies also change, so last year's tier may not hold.