How Health Insurance Prescription Drug Coverage Works

What is a formulary?

A formulary, sometimes called a prescription drug list (PDL), is the catalog of medications your plan covers. The formulary is developed by a committee of physicians and pharmacists working with the plan or its pharmacy benefit manager (PBM). It typically covers thousands of generic and brand-name drugs, organized into cost-sharing tiers.

If a drug is not on your plan's formulary, the plan may not cover it at all, or may require a formal exception process before approving coverage. You can find your formulary on your insurer's website, often searchable by drug name.

How do drug tiers work?

Drug tiers classify each covered medication by its cost-sharing level. Lower tiers have lower out-of-pocket costs, encouraging the use of generics and preferred drugs. Higher tiers reserve coverage for more expensive or complex medications, usually with a higher cost share.

Most employer plans use a 4 to 6 tier structure. A typical setup:

Specific tier counts and dollar amounts vary widely. Check your plan's Summary of Benefits or formulary document for the exact tier structure.

Copay vs coinsurance for drugs

Most plans use copaysA fixed dollar amount you pay for certain services (like office visits or prescriptions). Copay plans often have higher premiums but lower costs for routine care. Copays usually do not count toward your deductible, but they typically count toward your out-of-pocket maximum. for lower-tier drugs (a fixed dollar amount per fill) and coinsuranceAfter you reach your deductible, this is the percent of each bill you pay while insurance pays the remainder. for higher-tier and specialty drugs (a percentage of the drug's cost).

Coinsurance can produce dramatic variation in cost: a specialty drug that costs $5,000 with 30% coinsurance is $1,500 out of pocket per fill, while a $50 generic with a flat $10 copay is $10. For specialty drugs in particular, your out-of-pocket maxThe most you pay for covered medical bills in a year. After this, insurance pays 100% of covered costs. often becomes the practical cap on what you pay over the year.

For deeper context on these cost-sharing types, see copay vs coinsurance.

Do drugs count toward my deductible and out-of-pocket max?

Some plans have a separate prescription drug deductible that must be met before tier-based cost sharing kicks in. Others apply your drug costs to the same deductible as medical care. Read your Summary of Benefits to see which applies.

Under the Affordable Care Act, in-network costs for essential health benefits (including prescription drugs) must accumulate to a single annual out-of-pocket maximum, even if drugs are administered by a separate pharmacy benefit manager. This rule applies to non-grandfathered group health plans, which is most employer plans today.

What is prior authorization?

Prior authorization (PA)Approval from your insurer that must be obtained before certain prescriptions or medical services will be covered. Common for expensive drugs or services with lower-cost alternatives. is approval from your insurer that must be obtained before coverage is provided for certain drugs. It is most common for expensive medications, drugs with significant safety concerns, or drugs that have lower-cost alternatives. Your doctor submits clinical documentation to the insurer, who decides whether to approve coverage based on plan criteria.

If PA is denied, you have the right to appeal. Internal appeals go back to your plan; external appeals are reviewed by an independent third party. Many denials are reversed on appeal, especially with strong clinical documentation from your provider.

What is step therapy?

Step therapyAn insurer requirement that you try one or more lower-cost medications first before they cover a preferred drug. Exceptions can be requested based on medical necessity. (also called fail-first) requires you to try one or more lower-cost medications before your plan covers a preferred drug. If the first-step drug is ineffective, causes side effects, or is medically inappropriate, you can move to the next step or request an exception based on medical necessity. Many states have laws limiting how step therapy can be applied, particularly for chronic and serious conditions.

How does mail-order pharmacy work?

Most employer plans offer a mail-order pharmacy benefit, where you can fill a 90-day supply of maintenance medications and have them shipped to your home. Typical pricing: the 90-day mail-order copay is 2 to 2.5 times the 30-day retail copay, which means you pay for two months and get three. For long-term medications you take regularly, this can be a meaningful annual saving.

Mail-order is generally optional. Some plans, however, charge a higher copay or stop covering refills at retail pharmacies after a few fills of a maintenance drug, effectively pushing you to mail-order.

What about specialty drugs?

Specialty drugsA high-cost medication used to treat complex conditions like cancer or autoimmune disease. Typically placed in the highest formulary tier, often requires a specialty pharmacy and may need prior authorization. are high-cost medications used for complex conditions such as cancer, autoimmune diseases, hepatitis C, and certain rare diseases. They often require special handling, storage, or administration. Plans typically:

• Place specialty drugs in the highest formulary tier
• Use coinsurance instead of copay (often 20% to 50%)
• Require fills through a designated specialty pharmacy
• Require prior authorization and sometimes step therapy
• Limit quantities per fill

Manufacturer copay assistance programs and patient assistance foundations can help offset specialty drug costs, though some plans use “copay accumulator” policies that limit how this assistance counts toward your deductible or out-of-pocket max. Check your plan documents and ask your specialty pharmacy.

Compare plans with your prescription costs

Use the Health Plan Compare calculator to model total annual cost across plans, including your expected prescription spend. Look up each medication on each plan's formulary to confirm tier placement before deciding.

Related guides

• Copay vs coinsurance
• Deductible vs out-of-pocket max
• How to read a Summary of Benefits
• In-network vs out-of-network