Formularies & Drug Tiers

What this guide covers

Formularies & Drug Tiers explains how insurance plans list prescription drugs—and how those lists drive copays, rejections, and appeals. Beginner advocates use formularies to answer three questions: Is this drug covered at all? Which tier is it? Why is the patient paying $200 instead of $20?

Start with Prescription Coverage Basics if pharmacy vocabulary is new. This guide goes deeper on the drug list itself, not every appeal step.

This is educational information, not medical advice. Only the prescriber should choose which drug is clinically appropriate; advocates help match that choice to plan rules and exceptions.

What a formulary is

A formularyis the plan's list of drugs it will cover, with conditions. It is not the same as every drug on the market. Plans exclude some drugs entirely and place others on higher-cost tiers.

Each entry usually shows the drug name (brand and/or generic), strength and dosage form (tablet, injection, patch), a tier number or name, and restrictions such as prior authorization, step therapy, or quantity limits.

Two patients with the same diagnosis can pay different amounts if they are on different plans—or the same plan in a different calendar year.

How plans decide what is covered

PBMs & manufacturers

Pharmacy benefit managers negotiate rebates and prices with drug makers. A drug may land on a favorable tier because of contracts—not only because it is the best clinical choice. That is why a covered alternative sometimes costs the plan less and the patient less.

Clinical review

Plans also use pharmacy and therapeutics (P&T) committees to review safety and effectiveness. Drugs without good alternatives or with unique roles—some cancer or HIV medications—may stay on formulary at higher tiers rather than be excluded.

Annual & mid-year changes

Most plans publish a new formulary each plan year, often January 1. Drugs can move tiers, gain restrictions, or disappear. Some changes happen mid-year when generics launch or safety issues arise. Patients on auto-refill should check the new list before January shipments.

Drug tiers & what patients pay

Typical tier layout

Commercial and Part D plans use different labels, but patterns are similar. Tier 1 is usually preferred generics with the lowest copay. Tier 2 may be non-preferred generics or preferred brands. Tier 3 is often non-preferred brands. Tier 4 may carry higher coinsurance still.

The member handbook or drug list shows the copay or coinsurance for each tier. A $10 Tier 1 copay versus 25% coinsurance on Tier 4 can mean hundreds of dollars difference for the same condition.

Specialty tier

Many plans place high-cost biologics and oncology drugs on a specialty tier with percent coinsurance—sometimes 25–33% or more until out-of-pocket caps apply. These drugs often require a specialty pharmacy. See Specialty Pharmacy.

Not on formulary

If the drug is not listed, the plan treats it as uncovered unless you win a formulary exception. The pharmacy reject may say "drug not covered" even when a similar drug is on the list.

Restrictions on covered drugs

A drug can be on the formulary but still fail at the register when a restriction is not satisfied.

Prior authorization

The plan requires approval before paying. The prescriber submits clinical information. Guide: Rx Prior Authorization.

Step therapy

The plan requires trying one drug—often cheaper—before covering another. Guide: Step Therapy.

Quantity limits

The plan caps pills per month or refills per year. Guide: Quantity Limits.

Formulary listings show icons or abbreviations: PA, ST, QL. A drug on Tier 2 with PA is not truly ready to fill until authorization is on file.

How to look up a drug

Confirm the active plan—employer card, Part D plan name, or Medicaid managed care organization. Open the plan's drug search tool on the member portal or public formulary search. Enter the exact name, strength, and form; the plan may cover 40 mg tablets but not 20 mg. Note the tier, restrictions, and whether a preferred pharmacy affects price. Screenshot or print results with the date.

Medicare beneficiaries can use Medicare Plan Finder to compare Part D formularies by drug. Commercial members use the employer or insurer website.

Exceptions & lower tiers

When the formulary blocks the prescribed drug, advocates ask the plan for an exception—not a different pharmacy trick.

Formulary exception

Request coverage for a non-formulary drug because covered alternatives would be ineffective or harmful for this patient. Requires prescriber support. Full walkthrough: Formulary & Tiering Exceptions.

Tiering exception

Request a lower cost-sharing tier when the patient cannot use equally effective drugs on cheaper tiers—for example, side effects on every Tier 1 option.

Deadlines and forms differ by program. Medicare Part D uses coverage determination notices; commercial plans use PBM forms. See Medicare Part D Drug Appeals for Medicare-specific steps.

Medicare, Medicaid & commercial

Medicare Part D has standardized appeal rights and exception types with CMS oversight; the formulary must meet federal requirements. Medicaid often uses state preferred drug lists or managed care formularies, with fair hearing rights that vary by state. Employer and marketplace plans follow PBM formularies; appeals may follow plan documents and state insurance laws, and external review is sometimes available for fully insured plans.

Always identify the program before choosing forms. For Medicare orientation, see Medicare Part D in the Insurance topic.

What advocates should do

Compare covered alternatives

Ask the prescriber which drugs on lower tiers are clinically acceptable. Bring the formulary printout to appointments: "These three are Tier 1—does any work for you?"

Document clinical need

For exceptions, collect diagnosis, drugs already tried, side effects, and why the requested drug is necessary. Use Building a strong appeal packet habits—dates, chart notes, a short prescriber letter.

If the pharmacy rejected a claim, match the reject code to the restriction type before filing the wrong appeal. Roadmap: Denied Prescriptions.

Scenarios beginners run into

Drug dropped in January

The patient filled all year; a January reject says not covered. Check the new formulary, file a formulary exception quickly, or ask for a covered switch. Request temporary supply rules if the patient cannot stop the drug abruptly—under prescriber guidance.

Generic cheap, brand expensive

The pharmacist offers a generic at Tier 1; the prescriber wrote brand with dispense-as-written. Confirm whether the brand is medically required or whether the generic is acceptable. Request a tiering exception if only the brand works.

Same drug, two strengths

Ten mg may sit on Tier 2 while 20 mg is Tier 4 for the same brand. Search each strength separately. The prescriber may adjust dose to a covered strength if clinically appropriate.

Prescriber picked non-formulary drug

A new prescription goes electronically; the pharmacy rejects. Bring the formulary search to the clinic and ask for a formulary alternative or exception submission the same day.

Formulary says covered—still rejected

This is usually prior authorization not approved, step therapy not met, wrong member ID, or a preferred pharmacy issue—not a true formulary exclusion. Read the reject code. Do not file a formulary exception when prior authorization is the fix.

Medicare specialty tier coinsurance

The patient may hit 25–33% coinsurance until catastrophic coverage. Check manufacturer copay assistance (with Medicare limits), Medicaid wrap if dual-eligible, and Low Income Subsidy (Extra Help) status.

Related guides

Prescription Coverage Basics, Formulary & Tiering Exceptions, Rx Prior Authorization, Step Therapy, Quantity Limits, Denied Prescriptions, and Specialty Pharmacy.

Official resources

Medicare.gov — Part D formularies. Medicare.gov — Plan Compare (drug search). CMS — Part D plan basics.