Will your prescription actually be covered?

What a formulary is, and why it controls your bill

A formulary is the list of prescription drugs a health plan agrees to cover. Every plan has one, every formulary is different, and the formulary can change mid-year for non-grandfathered drugs. Two plans sold by the same insurer in the same ZIP code can put the same drug on different tiers — and the tier is what decides how much you pay.

Marketplace plans typically organize drugs into four or five tiers. The exact names and rules vary, but the structure is consistent:

• Tier 1 — Preferred generic. The lowest copay tier. Most plans charge a small flat copay (often $0–$15) even before you meet the deductible. About 90% of U.S. prescriptions are filled as generics, so this is where most people's drugs live.
• Tier 2 — Non-preferred generic / preferred brand. Either a generic the plan doesn't favor, or a brand the plan has negotiated good rebates on. Copays are still predictable but noticeably higher.
• Tier 3 — Non-preferred brand. Brand drugs the plan would rather you not use. Coinsurance often replaces a flat copay here, and the deductible usually has to be met before the plan pays anything.
• Tier 4 — Specialty. Biologics, oncology drugs, autoimmune therapies, and most newer injectables. Cost-sharing is almost always coinsurance (20%–40%), and a single prescription can exhaust your deductible by itself.
• Tier 5 — Preferred specialty (some plans). A second specialty tier with better cost-sharing, reserved for specialty drugs the plan has negotiated favorable contracts on.

Two things are easy to miss on a tier sheet. First: many plans apply the medical deductible to brand and specialty tiers, even though Tier 1 generics are covered at a flat copay from day one. Second: the same drug can sit on different tiers in two different plans from the same insurer. Tier is a contract negotiation, not a property of the molecule.

Prior authorization, step therapy, and quantity limits

Tier is just the price. There is a second layer of rules called utilization management that decides whether the plan will pay at all:

• Prior authorization (PA). The plan requires your prescriber to submit clinical justification before the drug is approved. Common on Tier 3+, brand-name drugs with cheaper alternatives, and most specialty drugs. A PA can take anywhere from 24 hours to several weeks to resolve.
• Step therapy (“fail first”). The plan won't cover a more expensive drug until you've tried — and failed on — a cheaper one. This is the rule behind the experience of being switched from one medication to another after starting a new plan.
• Quantity limits. Caps on how much of a drug the plan will pay for in a given period. Common on opioids, stimulants, and high-cost specialty drugs.
• Site of care restrictions. For infused drugs, plans may require administration at home or at a specific type of clinic rather than at a hospital, where the same drug is billed at multiples of the cost.

None of these rules necessarily mean the drug isn't covered. They mean there is a process in front of the coverage, and that process eats time — yours, your doctor's, and the pharmacist's. When you find a plan whose formulary lists your drug, search the same document for these utilization- management codes (often abbreviated “PA,” “ST,” or “QL” next to the drug name) before celebrating.

How to pressure-test a plan against your medication list

1. Make the list complete. Include everything you take regularly, including the OTC items your doctor told you to keep using (some — like prescription-strength omeprazole — are still on plan formularies). For each, note dose, frequency, and whether you take a brand or generic.
2. Check the plan formulary by name. Use the checker above for a quick yes/no on a specific medication. For a full picture, pull the plan's formulary PDF (every Marketplace plan publishes one) and search for each drug.
3. Note the tier and the utilization-management code. “Covered” on Tier 1 with no PA is what you want. “Covered” on Tier 4 with step therapy is a very different financial reality.
4. Estimate annual drug spend, not monthly. Multiply the copay or coinsurance by 12 (or however many fills per year). Compare that against the plan's drug deductible and out-of-pocket maximum. For specialty drugs, your true first-year cost is usually the out-of-pocket max — full stop.
5. Check the pharmacy network. Plans contract with specific retail and mail-order pharmacies. A 90-day mail fill at the preferred mail pharmacy is often half the cost of 30 days at a local pharmacy. If your plan offers it, use it.

Coverage gaps worth planning around

• GLP-1s for weight loss. Coverage is in flux. Many Marketplace plans cover GLP-1s for type 2 diabetes (Ozempic, Mounjaro) but exclude the weight-loss indications (Wegovy, Zepbound). Manufacturer self-pay programs and compounded versions have created a parallel cash market; the math now favors cash-pay in some scenarios.
• Brand-name insulin. Insulin pricing changed in 2023–2024; most major insulins are now available at $35/month or less through manufacturer programs even without insurance. Don't pay coinsurance against a $300 list price.
• ADHD stimulants. Coverage is intact but supply is intermittent. Quantity limits and pharmacy substitutions are routine. Build your plan choice around pharmacy access, not just insurance.
• Specialty biologics. The drug is almost always covered — the price is the question. If you take a biologic, the plan's out-of-pocket maximum is your real shopping criterion. Look at it before anything else.

Cash pay, manufacturer programs, and discount cards

Insurance is not always the cheapest path for a given drug. Three alternative routes are worth knowing:

• Manufacturer patient assistance programs. Almost every brand-name drug has one. For people with commercial insurance, copay cards bring brand-name drugs down to $0–$25 per fill on launch-priced therapies. The catch: copay cards can't be used with Medicaid or Medicare, and some plans use “copay accumulator” programs to prevent the copay-card payment from counting toward your deductible.
• Discount cards (GoodRx, SingleCare). Pharmacy benefit managers (PBMs) sell access to their negotiated rates outside of insurance. For Tier 3 brand drugs and many generics, the GoodRx cash price is lower than the insurance copay. Discount-card purchases do not count toward your deductible or out-of-pocket max, so this is best used for predictable, low- volume needs.
• Direct-to-consumer pharmacies. Mark Cuban Cost Plus Drug Company, Amazon Pharmacy's RxPass, and a growing list of others sell generics at cost-plus markups. Worth checking for chronic generics where price stability matters.

The general rule a clinician would give you: insurance is best for the expensive, unpredictable stuff (specialty, hospital, emergency); cash and discount programs are often better for predictable generics and brand-name drugs with active manufacturer programs. Don't assume the insurance path is cheapest just because it's the default.