Drug Formulary Tiers: Why Your Copay Depends on the Tier

A formulary tier is the cost category your insurance plan assigns to a specific drug, and it largely determines your copay. A formulary is the list of drugs a plan covers, and plans typically sort those drugs into tiers, from lowest-cost generics to highest-cost specialty drugs (HealthCare.gov). Two people on the same drug can pay very different copays if their plans place it in different tiers. Comparing prescription prices can help when a drug lands in a high tier.

What a formulary tier actually controls

Your health plan's formulary is its official list of covered medications. Within that list, most plans group drugs into tiers, and each tier carries its own cost-sharing amount, either a flat copay or a percentage coinsurance. According to KFF's 2025 Employer Health Benefits Survey, the vast majority of workers with employer coverage are enrolled in a plan with tiered prescription cost sharing, and most have four or more tiers (KFF). That means your out-of-pocket cost for a specific prescription depends heavily on where that drug sits on your plan's list, not just on the drug's retail price.

How tiers are typically structured

Tier structures vary by insurer, but a common pattern looks like this:

Older KFF data found that among workers in plans with three or more tiers, the average copay was roughly $11 for the first tier, $37 for the second, $67 for the third, and $116 for the fourth (KFF). These are averages, not guarantees, and actual amounts depend entirely on your specific plan.

Medicare Part D plans use a similar tiered approach, and the government's official site explains how these plans decide what a drug costs based on its formulary placement (Medicare.gov).

Why the same drug can land in different tiers

Tier placement is set by the insurer or its pharmacy benefit manager, not by the FDA or by how effective a drug is. A few reasons the same medication might be priced differently across plans:

• Rebate deals. Manufacturers negotiate rebates with pharmacy benefit managers, and drugs with bigger rebates sometimes get more favorable tier placement.
• Therapeutic category competition. If several similar drugs treat the same condition, a plan may favor the one with the best negotiated price.
• Generic availability. A drug with a generic version available may get pushed to a higher tier to steer patients toward the generic.
• Specialty classification. Complex, high-cost drugs, including many biologics, are usually carved into their own specialty tier regardless of whether a generic or biosimilar exists.

This is one reason it pays to check your plan's specific formulary before assuming a drug will be cheap just because it is a generic, or expensive just because it is a brand name. You can also look at how prices compare across pharmacies with BetterBuyRx's price comparison tool, since cash prices vary independently of your plan's tier system.

What to do if a drug's tier is costing you too much

If your copay for a specific drug seems high, a few options can help:

• Check the formulary before you fill. Most insurers post a searchable formulary online or through your member portal.
• Ask about a tiering exception. If a higher-tier drug is medically necessary and a lower-tier alternative would not work for you, your doctor can request a formulary exception. Approval depends on your plan's criteria and is not automatic.
• Ask your doctor about lower-tier alternatives. A different drug in the same class might treat your condition and sit in a lower tier. Only your doctor or pharmacist can advise on whether switching makes sense for you.
• Compare the cash price. Sometimes a discount card or cash price beats your insurance copay, especially for lower-cost generics. See our guide on prescription discount cards for more on how that works.

Search your medication on BetterBuyRx to compare pharmacy prices before you decide how to pay for a high-tier drug.

Specialty tiers deserve extra attention

Specialty tiers cover the most expensive category of drugs, often used for complex chronic conditions. These tiers commonly use coinsurance, a percentage of the drug's cost, rather than a flat copay, which means your out-of-pocket cost can swing with the drug's price. If you are prescribed a specialty medication, ask your plan about any out-of-pocket caps for that tier, and ask your doctor's office whether a manufacturer copay card or patient assistance program might apply. These programs are separate from your formulary tier but can offset what you owe.

Formulary tiers are not the whole story

Tier placement tells you part of the cost picture, but your deductible status also matters. If you have not met your deductible yet, you may pay the full negotiated price for a drug regardless of its tier, since tier-based copays and coinsurance typically kick in only after the deductible is met. For more on that interaction, see our guide on why prescriptions cost more before you meet your deductible. It also helps to understand who sets these lists in the first place. Pharmacy benefit managers build and manage most formularies on behalf of insurers, and their negotiations with drug makers directly shape tier placement. Read more in our explainer on what a PBM is.

Compare prescription prices on BetterBuyRx anytime your formulary tier leaves you with a copay that feels too high.