Formulary 101: How to Read Your Insurance Drug List

When people try to figure out if their insurance covers a GLP-1 medication like Wegovy or Zepbound, one of the first places to look is the formulary. Most people have never heard this word before their doctor or pharmacist mentions it. It sounds technical, but the concept is simple.

Your formulary is your insurance plan's official list of covered drugs. If a medication is on the list, your plan will help pay for it (subject to your cost-sharing). If it's not on the list, your plan generally won't cover it — unless you request an exception.

Here's how to find your formulary, read it, and figure out what it means for your medication.

What a Formulary Is (and Isn't)

A formulary is not a complete list of every drug that exists. It's not a list of drugs your doctor recommends. It's not a list of drugs that are safe or effective.

A formulary is a list of drugs your specific insurance plan has agreed to cover, negotiated with drug manufacturers, and priced according to their internal tier system. Plans design formularies to balance coverage with cost — they negotiate discounts with certain manufacturers and often prefer (or require) those drugs over similar alternatives.

Two plans from the same insurance company can have different formularies. Your plan's formulary this year may not be the same as last year's. This is why you can't assume a medication is covered just because it was covered before, or because someone you know with "the same insurance" has coverage.

How Tiers Work

Most formularies are organized into tiers — usually numbered 1 through 4 or 5, sometimes labeled with words like "generic," "preferred brand," and "non-preferred brand." Here's how those typically break down:

Tier 1 — Generic drugs The lowest-cost tier. These are generic versions of medications where the patent has expired. Your copay or coinsurance here is usually low.

Tier 2 — Preferred brand-name drugs Brand-name drugs that your insurer has negotiated a discount on. These are the insurer's preferred choices within a drug class. Cost-sharing is higher than Tier 1 but lower than Tier 3.

Tier 3 — Non-preferred brand-name drugs Brand-name drugs your insurer covers but hasn't negotiated favorable rates on. Cost-sharing can be significantly higher here.

Tier 4 and above — Specialty drugs High-cost drugs — often biologics, specialty injectables, or newer branded medications. GLP-1s for obesity, like Wegovy and Zepbound, frequently fall into this tier or are in a specialty category. Cost-sharing is highest here, sometimes structured as a percentage of the drug's cost (coinsurance) rather than a flat copay.

Not covered / excluded Some drugs simply aren't on the formulary at all. Many insurance plans explicitly exclude weight-loss medications or obesity drugs as a category. If that's the case for your plan, you'll need to pursue a formulary exception, switch plans, or explore other options.

How to Find Your Plan's Formulary

Your formulary is a public document. Here's where to find it:

• Your insurance company's website. Log in to your member portal and look for "drug list," "formulary," or "prescription benefits." Most insurers have a drug search tool where you can type in a medication by name.
• Your Summary of Benefits and Coverage (SBC). This is the standardized document you received when you enrolled. It gives a high-level overview of drug tiers and cost-sharing.
• Your plan documents. The full evidence of coverage or plan booklet will include formulary information or a link to it.
• Your pharmacy. Ask your pharmacist to run a test claim for your medication. They'll be able to see whether it's covered under your plan and at what tier.
• Call member services. If you can't find the formulary online, call the number on the back of your insurance card and ask directly. Tell them the specific drug name and ask whether it's covered, at what tier, and whether prior authorization is required.

Reading a Formulary Entry

Once you find your medication on the formulary (or confirm it's not listed), here's what to look for:

Coverage status Is it covered? Some formularies show medications as "covered" with restrictions, or "not covered" outright. If it says "not covered" or doesn't appear, that's significant.

Tier Which tier is it on? This tells you roughly what your cost-sharing will be.

Restrictions This is often the most important column. Common restrictions include:

• PA (Prior Authorization): You need approval before the plan will pay
• ST (Step Therapy): You must try another medication first
• QL (Quantity Limits): The plan will only cover a certain amount per month or fill

GLP-1 medications that are covered typically come with at least one of these restrictions — most often PA, and frequently QL as well. Finding your medication on the formulary doesn't mean it's automatically approved; it means approval is possible with the right process.

What to Do if Your GLP-1 Isn't on the Formulary

If you search your formulary and your prescribed medication doesn't appear — or appears as "not covered" — you have options:

1. Request a formulary exception You can ask your insurer to cover a non-formulary drug as an exception. This requires a letter from your doctor explaining why the covered alternatives are not appropriate for you. The standard is "medical necessity" — your doctor needs to make the case that the non-covered drug is the right choice for your specific situation, and that covered alternatives won't work.

2. Check if a similar medication is covered If Wegovy isn't covered but Saxenda is, ask your doctor whether switching would be medically reasonable. If Zepbound isn't covered but another tirzepatide formulation is on the formulary (under a different indication), ask about that. Your doctor knows the clinical nuances here better than anyone.

3. Look at the plan's exclusion policies Some plans exclude all weight-loss or anti-obesity medications as a category. This is often stated clearly in the plan documents under "exclusions." If obesity medications are categorically excluded, a formulary exception is unlikely to succeed — your options are appeal, switching plans, or exploring manufacturer assistance programs.

Even if the medication is listed on the plan's formulary, for some plans, certain medications can be excluded by name (such as Zepbound) or by indication (such as obesity, chronic weight management, or weight loss). This is particularly true of employer-sponsored health plans that adopt a formulary but customize their plan beyond the formulary.

4. Consider this during open enrollment If your current plan doesn't cover your medication, open enrollment is your opportunity to switch to a plan that does. Before selecting a plan, look up any medication you need in that plan's formulary. See our article on how to pick a plan that covers your medication.

Quantity Limits: What They Mean for GLP-1s

Quantity limits (QL) define how much of a medication your plan will cover per month. For injectable GLP-1s like Wegovy and Zepbound, this typically means the plan covers one auto-injector pen (four doses) per 28-day supply.

If your doctor changes your dose — say, you're moving to a higher maintenance dose — make sure the PA on file reflects the correct dose and quantity. Quantity limit denials are often resolved quickly by submitting an updated prior authorization for the correct dose.

The Bottom Line

Your formulary is the foundation of your medication coverage. Before you can fight for coverage, you need to know what your plan says. Find your formulary, search for your medication by name, and note the tier and any restrictions listed. Many insurance companies and pharmacy benefits managers have patient portals where medication coverage can be searched by patients (unfortunately not by providers).

If the medication is on the formulary with a prior authorization requirement, that's actually a good sign — it usually means coverage is possible, and your doctor can pursue it. If it's not on the formulary at all, you have more work to do — but it's not necessarily the end of the road.

When in doubt, your doctor's office, insurance/PBM portal, and your insurance company's member services line are your best resources for getting clarity.