What Is a Drug Formulary? Prescription Tiers Explained
Your health plan's formulary determines which drugs are covered and at what cost. Here's how tiers work and what to do when your medication is denied.
What Is a Drug Formulary? Prescription Tiers Explained
If you've ever had a prescription denied or discovered your medication costs significantly more than expected, the reason often comes down to your plan's formulary — the list of drugs your insurance covers and at what tier.
What Is a Formulary?
A formulary (also called a drug list or preferred drug list) is the list of prescription drugs covered by your health insurance plan. It is developed by your insurer's Pharmacy Benefit Manager (PBM) and is reviewed and updated regularly (usually quarterly or annually).
Not all drugs are on every formulary, and the position a drug occupies on the formulary determines how much you pay for it.
How Formulary Tiers Work
Most health plans use a tiered formulary structure. The most common structure has 4–5 tiers:
| Tier | Drug Type | Your Cost |
|---|---|---|
| Tier 1 | Preferred generics | Lowest copay ($0–$15) |
| Tier 2 | Non-preferred generics / preferred brands | Low-moderate copay ($20–$50) |
| Tier 3 | Non-preferred brand names | Moderate copay ($50–$100) |
| Tier 4 | Preferred specialty drugs | High copay / coinsurance |
| Tier 5 | Non-preferred specialty drugs | Highest cost (often 25–33% coinsurance) |
Some plans add a Tier 6 for certain ultra-high-cost biologics or gene therapies.
The higher the tier, the more you pay out of pocket. Plans design tiers to encourage the use of lower-cost alternatives.
Non-Formulary Drugs
If your prescribed medication is not on the formulary at all, the plan typically will not cover it — or will cover it at very high cost. This is a common source of prescription denials.
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Why Your Drug May Not Be Covered
- Not on the formulary: The drug simply isn't listed — newer drugs, certain brand-name drugs, or medications the PBM didn't negotiate a price for.
- Tier placement requires higher cost-sharing: The drug is covered, but at a high-cost tier.
- Prior Authorization Denied: How to Appeal" class="auto-link">Prior authorization required: Certain drugs (especially specialty drugs and biologics) require PA before the plan will cover them.
- Quantity limits: The plan limits how much of a medication it will cover per prescription fill or per month.
- Step therapy: You must try lower-tier alternatives first.
How to Get Coverage for a Non-Formulary Drug
Formulary exception request: Most plans must allow you to request an exception that places your drug at a lower tier or adds it to the formulary for your specific medical needs. Your physician must submit a letter of medical necessity explaining:
- Why the non-formulary drug is necessary for your condition
- Why covered alternatives are not clinically appropriate for you (contraindications, prior failures, unique clinical needs)
Under the ACA, plans must have a process for formulary exceptions and must respond within defined timeframes.
Step therapy exception: If denied for not completing step therapy, your doctor can argue:
- The required drugs are contraindicated
- You previously tried and failed those alternatives
- Your condition requires the specific drug your doctor prescribed
Check next year's formulary: If a drug was removed from your formulary at plan renewal, check whether it was on the formulary when your doctor first prescribed it. Continuity-of-care protections may apply.
Shopping for Better Formulary Coverage
If your medication is consistently not covered or very expensive:
- During open enrollment, compare plans specifically by formulary coverage for your medications
- Use your insurer's online formulary tool — most plans publish their drug list
- Check GoodRx and other discount programs — sometimes cash price is lower than your insurance cost-share for generic drugs
Fight Back With ClaimBack
ClaimBack helps you build a formulary exception request or step therapy appeal, so you can get the medication your doctor prescribed at a price you can afford.
Start your appeal at ClaimBack
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