When you're about to write a prescription, the last thing you want is for your patient to walk out of the office only to find out their medication isn't covered-or worse, costs $200 out-of-pocket when they expected $5. That’s why checking the formulary before prescribing isn’t optional. It’s routine. And it’s faster than you think-if you know where to look and what to look for.
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 insurance plan. It’s not just a catalog. It’s a carefully curated selection of drugs approved by teams of doctors and pharmacists based on safety, effectiveness, and cost. Every Medicare Part D plan, Medicaid program, and commercial insurer has one. And they change-often. Formularies are broken into tiers. Most have three to five levels. The lower the tier, the less the patient pays. Tier 1 usually means preferred generics-think metformin or lisinopril-costing $1 to $5 per prescription. Tier 5? That’s specialty drugs like insulin glargine or cancer therapies, where patients pay 25% or more of the full price. Some drugs come with extra rules: PA (prior authorization), ST (step therapy), or QL (quantity limit). If you don’t check for these, your prescription gets rejected. The patient waits. The clinic gets a call. Everyone loses time.How Formularies Differ Between Plans
Not all formularies are the same. Medicare Part D plans follow federal rules and typically use a five-tier structure. But commercial insurers like UnitedHealthcare or Aetna might use four tiers. Medicaid is even more variable-42 states have closed formularies, meaning if a drug isn’t on the list, you need prior authorization just to try it. In open formularies, you have more freedom, but you still pay higher costs if you choose non-preferred drugs. Here’s a quick example: Januvia (sitagliptin). One Medicare plan lists it as Tier 3-preferred brand. Another calls it Tier 4-non-preferred. A third requires step therapy: the patient must try metformin first, and fail, before Januvia gets approved. If you prescribe it without checking, you’re setting up a delay. And delays in diabetes care? That’s dangerous.Where to Check Formularies: The Practical Guide
You have three main ways to check a formulary before prescribing:- Insurer’s website-Most plans have a drug search tool. For Medicare, go to the plan’s official site, enter the patient’s zip code and plan name, then type in the drug. Aetna’s tool, for example, shows tier level, PA status, and step therapy requirements in seconds. It’s accurate, real-time, and free.
- Your EHR system-If your clinic uses Epic, Cerner, or another modern system, check if it has an embedded formulary checker. Northwestern Medicine cut prescription abandonment by 42% after adding Epic’s Formulary Check module. That’s not a gimmick-it’s a workflow upgrade.
- CMS Plan Finder-For Medicare patients, this is your go-to. It covers 99.8% of Part D plans. Just enter the patient’s name, address, and drugs. It shows exactly what’s covered, at what cost, and what restrictions apply.
What to Look for When You Check
When you pull up a drug on a formulary, pay attention to four things:- Tier level-This tells you the out-of-pocket cost. A Tier 1 drug might be $5. A Tier 4? $60 or more.
- PA (Prior Authorization)-The prescriber must submit documentation to prove medical necessity. This can take 24 to 72 hours. For cancer drugs, delays of over 48 hours happen in 32% of cases.
- ST (Step Therapy)-The patient must try and fail on a cheaper alternative first. Common with antidepressants, biologics, and asthma inhalers.
- QL (Quantity Limit)-You can’t prescribe a 90-day supply if the plan only allows 30 days. You’ll have to call in a second prescription.
Why This Matters More Than Ever in 2026
Starting January 1, 2026, Medicare Part D plans are required to use Real-Time Benefit Tools (RTBT). That means formulary and cost data will pop up automatically in your EHR as you type a drug name. It’s coming. But not all systems are ready yet. And even when they are, you still need to know how to interpret the data. The Inflation Reduction Act’s $2,000 annual cap on out-of-pocket drug costs for Medicare beneficiaries is already reshaping formularies. In 2025, 73% of Medicare Part D plans moved more drugs to lower tiers to help patients hit that cap faster. That means drugs you used to prescribe as Tier 3 might now be Tier 1. Or vice versa. You can’t assume last year’s list still applies. And here’s the hard truth: 68% of U.S. clinicians spend 10 to 20 minutes per patient just verifying coverage. That’s 200+ hours a year per provider. If you don’t have a system, you’re wasting time. And your patients are paying the price in delays.
Pro Tips to Save Time and Avoid Errors
- Bookmark the formulary pages for your most common insurers. UnitedHealthcare, Aetna, and Humana all have direct URLs to their 2024/2025 drug lists. Save them in your browser.
- Set quarterly calendar alerts for formulary updates. Most insurers update in January, April, July, and October. HealthPartners, for example, publishes monthly changes.
- Use the insurer’s provider hotline-98% of Medicare Part D plans offer 24/7 support. Call if the website is unclear. It’s faster than waiting for an email reply.
- Train your staff-A medical assistant can verify coverage before the patient even sees you. That cuts your workload and improves patient satisfaction.
- Know your exceptions-Medicare requires insurers to respond to prior authorization requests within 72 hours for standard cases and 24 hours for urgent ones. If you’re waiting longer, call them.
What Happens When You Skip the Check?
A 2024 American Medical Association report found that 88% of physicians have seen care delayed because of prior authorization. In 34% of those cases, the delay led to serious harm-worsening diabetes, uncontrolled hypertension, or hospitalizations. One patient in a Reddit thread described how a missed formulary check led to a 10-day gap in insulin. She ended up in the ER. It’s not just about cost. It’s about safety. A drug that’s safe and effective in theory can be dangerous in practice if the patient can’t afford it-or can’t get it in time.Final Thought: Make It a Habit
Checking formularies isn’t a chore. It’s part of prescribing. Just like checking allergies or renal function. You wouldn’t prescribe a nephrotoxic drug to someone with kidney disease without thinking twice. Don’t prescribe a $120 drug to someone on a fixed income without checking if it’s covered. Start with one patient today. Open the insurer’s website. Type in the drug. Look at the tier. Check for PA or ST. Tell the patient what to expect. You’ll save time. You’ll save stress. And most importantly, you’ll save your patient from a bad surprise.Do all insurance plans have formularies?
Yes. Every Medicare Part D plan, Medicaid program, and commercial health plan uses a formulary to control costs and guide prescribing. Even Medicare Advantage plans with drug coverage include one. The structure and rules vary, but the list exists for every plan.
Can I prescribe a drug that’s not on the formulary?
Yes-but the patient will likely pay much more, or the claim will be denied. For closed formularies (common in Medicaid), you must request prior authorization to use a non-formulary drug. Even in open formularies, non-preferred drugs often fall into the highest tier, meaning the patient pays 40% or more of the cost. Always check first.
How often do formularies change?
Medicare Part D plans must give 60 days’ notice before removing or restricting a drug. Many insurers update quarterly-in January, April, July, and October. Some, like HealthPartners, publish monthly updates. Commercial plans can change more frequently. Always verify the current version before prescribing.
What’s the difference between a tier and a prior authorization?
A tier determines how much the patient pays out of pocket-lower tier, lower cost. Prior authorization (PA) is a separate requirement: you must submit documentation to prove the drug is medically necessary before the plan will cover it. A drug can be on Tier 1 and still require PA. Or it can be Tier 4 with no PA. They’re independent rules.
Is there a free tool I can use to check all formularies at once?
No single tool checks every insurer, but CMS’s Plan Finder covers nearly all Medicare Part D plans for free. For commercial plans, you’ll need to check each insurer’s website individually. EHR-integrated tools like Epic’s Formulary Check are the closest thing to a universal solution-but only if your clinic uses them.
Why do different Medicare plans cover the same drug differently?
Each Medicare Part D plan is run by a private insurer (like Aetna, Humana, or UnitedHealthcare), and they design their own formularies within CMS guidelines. They can choose which drugs to include, which tier to put them in, and what restrictions to apply. That’s why Januvia might be Tier 3 on one plan and Tier 4 on another. Always check the patient’s specific plan.
What’s the best way to avoid delays with prior authorization?
Use the insurer’s online portal to submit PA requests immediately after prescribing. Many offer e-PAs that auto-fill with your EHR data. Always include supporting documentation-lab results, previous treatment failures, or specialist notes. And call the provider line if it’s been over 48 hours. For urgent cases (like cancer or unstable diabetes), request expedited review.