How to Check Formularies and Preferred Drug Lists Before Prescribing

Before you write a prescription, you need to know if the drug is covered-and how much the patient will actually pay. It’s not just about what’s clinically right. It’s about what’s covered, what requires prior authorization, and whether the patient can afford it. If you skip this step, you risk delayed treatment, patient non-adherence, or even an emergency visit because they couldn’t fill the script.

What Exactly Is a Formulary?

A formulary, also called a Preferred Drug List (PDL), is the official list of medications covered by a patient’s health plan. It’s not random. Every drug on it has been reviewed by a committee of doctors and pharmacists who look at safety, effectiveness, and cost. These lists are updated regularly-sometimes monthly-because new drugs hit the market, generics become available, or prices change.

Medicare Part D plans, for example, must follow strict federal rules. They use a five-tier system:

• Tier 1: Preferred generics-usually $1 to $5 per prescription
• Tier 2: Other generics-slightly higher cost
• Tier 3: Preferred brand-name drugs-clinically proven, but more expensive
• Tier 4: Non-preferred brands-often $50 or more per script
• Tier 5: Specialty drugs-costing over $950/month, paid as a percentage (coinsurance)

But here’s the catch: formularies vary by plan. Two patients on the same Medicare plan might have different formularies if they’re enrolled through different insurers. One might cover Januvia as Tier 3. Another might require step therapy first. And a third might not cover it at all.

How to Find the Right Formulary

You can’t guess. You have to look it up-for each patient, each time.

Start with the insurer’s website. Most have a drug search tool. For Aetna, you enter the patient’s county and plan name. For UnitedHealthcare, you pick the plan type (Medicare, Commercial, etc.) and search by drug name. You’ll see the tier, any restrictions (like prior authorization), and sometimes even estimated out-of-pocket costs.

If the website is slow or confusing, download the full PDF formulary. Many insurers, like Excellus BCBS, offer downloadable PDFs that list every drug and its status. Bookmark the direct link to the current year’s formulary. Medicare plans for 2024 are effective January 1, 2024, through December 31, 2024-but they can change mid-year with 60 days’ notice.

For Medicaid patients, it’s state-specific. Minnesota, for example, has a single PDL for all Medicaid members. California has a different one. You need to know which state’s program the patient is enrolled in.

And don’t forget the CMS Plan Finder tool. It covers 99.8% of Medicare Part D plans. You can search by drug, zip code, and plan type. It’s free, official, and updated daily.

Understanding the Codes: PA, ST, QL

Don’t just look at the tier. Look at the codes next to the drug:

• PA (Prior Authorization): You must submit paperwork before the plan will approve the drug. This can take 24-72 hours. For cancer drugs, delays over 48 hours happen in 32% of cases.
• ST (Step Therapy): The patient must try and fail on a cheaper drug first. Example: You want to prescribe a new diabetes drug, but the plan requires the patient to try metformin first-even if they’ve already tried it and it didn’t work.
• QL (Quantity Limit): The plan limits how much you can prescribe in a month. Example: Only 30 tablets of a painkiller per 30 days, even if the patient needs more.

These aren’t just bureaucratic hurdles. They directly impact care. A 2024 AMA report found 88% of physicians have seen treatment delays because of prior authorization. In some cases, those delays led to serious harm.

Medicare vs. Medicaid vs. Commercial Plans

Not all formularies are built the same.

Medicare Part D plans are standardized across the country. They must cover at least two drugs per therapeutic class and offer exceptions. They use the five-tier model. They’re required to respond to prior authorization requests in 72 hours (24 for urgent cases).

Medicaid programs are run by states. 42 states use closed formularies-meaning if a drug isn’t on the list, it’s blocked unless you get an exception. That’s harder than it sounds. The process can take days or weeks.

Commercial plans (like those from UnitedHealthcare or Aetna for employer coverage) are all over the map. Some use four tiers. Others have six. Some don’t even publish their formularies publicly. You might need to call the provider line.

The bottom line: you can’t use the same checklist for every patient. A drug that’s Tier 1 in one plan might be Tier 4-or not covered at all-in another.

How to Save Time: Tools That Actually Work

Checking formularies manually for every patient takes time. A 2023 Sermo survey found primary care physicians spend nearly 19 minutes per patient just verifying coverage.

The good news? There are tools that cut that time in half.

EHR-integrated formulary checkers are the most effective. Northwestern Medicine reduced prescription abandonment by 42% after adding Epic’s Formulary Check module. It shows tier level, PA requirements, and cost estimates right in the prescription screen. If the drug isn’t covered, it suggests alternatives.

Real-time benefit tools (RTBT) are coming fast. By January 1, 2026, Medicare Part D plans must integrate RTBT into EHRs. That means when you click “prescribe,” the system will pull live data from the patient’s plan-cost, tier, restrictions-all in seconds.

If your clinic doesn’t have this yet, use these workarounds:

• Bookmark the top 5 insurer formulary pages you use most
• Set calendar reminders for quarterly updates (HealthPartners, for example, updates in January, April, July, October)
• Keep a printed copy of your most common formularies in your exam room
• Use the insurer’s 24/7 provider hotline-98% of Medicare plans offer this

What Happens When You Don’t Check

I’ve seen it too many times. A patient comes in with a new script. They’re excited. They leave the office thinking they’re getting a great new drug. Then they get to the pharmacy and are told, “It’s not covered.” Or, “You need to try something else first.” Or, “That’s $280 out of pocket.”

They don’t fill it. They don’t call back. They stop taking their meds. Their blood pressure spikes. Their diabetes gets worse. A few months later, they’re back in the ER.

This isn’t rare. A 2024 study showed that 28% of Medicare beneficiaries experience formulary changes mid-year. Patients get confused. Providers get blamed.

The fix? Make formulary checks part of your routine-like checking allergies.

What’s Changing in 2025 and Beyond

The Inflation Reduction Act’s $2,000 annual cap on out-of-pocket drug costs for Medicare starts in 2025. That’s forcing insurers to shift drugs to lower tiers. More generics. Fewer specialty drugs in Tier 5. More drugs in Tier 1.

AI tools are also entering the space. Epic’s FormularyAI, launched in August 2024, predicts coverage likelihood with 87% accuracy by analyzing 10 million past prior authorization decisions. It doesn’t replace you-it helps you decide faster.

But challenges remain. Therapeutic interchange programs (where pharmacists swap a prescribed drug for a cheaper one on the formulary) are growing. Some say it saves money. Others say it undermines patient trust. There’s no national standard yet.

Final Checklist Before Prescribing

Before you hit “submit,” run through this:

1. Confirm the patient’s exact insurance plan (Medicare Part D? Medicaid? Employer plan?)
2. Search the insurer’s official formulary website or use CMS Plan Finder
3. Check the tier level-this tells you the cost
4. Look for PA, ST, or QL codes-these are red flags
5. Verify the formulary is current (effective Jan 1-Dec 31, 2024, unless updated)
6. If unsure, call the insurer’s provider line-don’t guess
7. Document your check in the patient’s chart: “Formulary verified per Aetna 2024 PDL, Tier 3, no restrictions”

This isn’t extra work. It’s part of prescribing responsibly. The right drug, at the right price, at the right time-before the patient ever leaves your office.