How to Check Drug Coverage Tiers and Formulary Changes for Medicare Part D

Every year, millions of seniors face unexpected spikes in their medication costs-not because their prescriptions changed, but because their insurance plan did. If you're on Medicare Part D or a private plan with a drug formulary, you're likely paying different amounts for the same drug depending on which tier it's in. And those tiers? They can shift without warning. Knowing how to check your drug coverage tiers and spot formulary changes isn’t just helpful-it’s essential to avoid surprise bills.

What Is a Drug Formulary and Why Does It Matter?

A drug formulary is simply the list of medications your insurance plan covers. But it’s not just a simple list. It’s broken into tiers, and each tier has a different cost to you. Tier 1 is usually the cheapest-often generic drugs with a $5 or $10 copay. Tier 5? That’s where specialty drugs like GLP-1 weight loss medications (Wegovy, Ozempic) land, with coinsurance that can hit $300 or more per month.

The system was designed to save money for insurers, but it also pushes patients toward cheaper alternatives. The problem? Many seniors don’t realize their blood pressure pill or diabetes med moved from Tier 1 to Tier 3 overnight. One user on Medicare.gov reported their monthly cost jumped from $10 to $55 after a formulary update. That’s not a rare case.

How Tiers Work: 3, 4, or 5 Levels?

Not all plans use the same structure. Most have either 3, 4, or 5 tiers. Here’s what you’re likely to see:

• Tier 1: Preferred generics. Lowest cost. Often under $10.
• Tier 2: Non-preferred generics or lower-cost brand-name drugs. Around $15-$30.
• Tier 3: Higher-cost brand-name drugs. No generic available yet. Can be $50-$100.
• Tier 4: Non-preferred brand-name drugs with alternatives in lower tiers. Often require prior authorization.
• Tier 5: Specialty drugs. Injectables, infusions, or high-cost treatments. Coinsurance can be 33% or more of the total price.

The exact names vary. Some plans call Tier 1 “preferred generics,” others say “standard generics.” But the cost pattern stays the same: lower tier = lower you pay.

How to Check Your Drug’s Tier Right Now

You don’t need to wait for a letter. Here’s how to check your coverage in under 10 minutes:

1. Find your plan’s official website. Look for “Drug Formulary,” “Formulary Search,” or “Prescription Drug List.”
2. Use the search tool. Type in your exact medication name-brand or generic. Don’t guess. If you take Lisinopril, search for that, not “blood pressure pill.”
3. Check the tier. It will say something like “Tier 2” or “Preferred Brand.”
4. Look at the cost. It should show your copay or coinsurance amount.
5. See if prior authorization or step therapy is required. If it says “Requires Prior Auth,” your doctor must submit paperwork before the plan pays.

Most major plans-Cigna, Humana, UnitedHealthcare, Excellus BCBS-have these tools online. If you’re on Medicare Part D, go to Medicare.gov and use the Plan Finder tool. Enter your drugs, zip code, and pharmacy. It compares all plans in your area and shows you exactly where each drug falls.

When Formularies Change (And How You’ll Know)

Plans can change their formularies anytime-but there are rules. By law, they must notify you if they:

• Remove a drug completely
• Move your drug to a higher tier
• Add a new requirement like prior authorization

They have to send you a letter at least 60 days before the change takes effect. But here’s the catch: if a drug is pulled for safety reasons (like a recall), they can act faster. And if a new generic hits the market, they might move your brand-name drug to a higher tier immediately.

The biggest change trend in 2025? GLP-1 drugs like Wegovy and Mounjaro. Many plans moved them to Tier 5 or added strict prior authorization. Some seniors are now paying $400+ a month for drugs they used to get for $50. If you’re on one of these, check your formulary every 3 months.

What to Do If Your Drug Gets Moved to a Higher Tier

Don’t panic. You have options:

• Ask your doctor for a generic alternative. If there’s a cheaper version on Tier 1, they can switch you. Many drugs have multiple generics.
• Request a formulary exception. You can ask your plan to cover your drug at a lower tier if it’s medically necessary. Your doctor fills out a form. Approval rates range from 55% to 82%, depending on your plan and evidence provided.
• Use a 30-day transition supply. If your drug is being removed or tiered up, most plans must give you a 30-day supply while you and your doctor figure out next steps.
• Call your pharmacist. They know what’s covered and can suggest alternatives you might not know about.

One senior in New York saved $200 a month when her pharmacist suggested switching from a non-preferred brand to a preferred generic with the same active ingredient. She didn’t even need a new prescription.

How to Stay Ahead of Changes

Formularies aren’t static. They change every January-and sometimes mid-year. Here’s how to avoid getting caught off guard:

• Check your formulary every January when new plans start.
• Set a calendar reminder to review your drugs every 3 months.
• Sign up for plan notifications via email or text. Most insurers let you opt in.
• Keep a printed or digital list of your drugs and their current tiers.
• Use free help: Your State Health Insurance Assistance Program (SHIP) offers free, one-on-one counseling. They helped 1.7 million people in 2022.

Common Mistakes Seniors Make

Most people don’t realize how easy it is to overpay:

• Assuming your drug is still covered the same way after plan renewal.
• Not checking if your pharmacy is in-network. Even if the drug is covered, you might pay more at an out-of-network pharmacy.
• Ignoring prior authorization. If your plan requires it and you don’t get approval, you’ll pay full price.
• Not knowing the difference between copay and coinsurance. Copay is a fixed fee. Coinsurance is a percentage of the drug’s total cost. For a $1,000 specialty drug, 30% coinsurance = $300.

When to Switch Plans

If your top 3 medications moved to higher tiers and you can’t get exceptions, it’s time to switch. Medicare’s Annual Enrollment Period runs from October 15 to December 7. You can switch plans to one that covers your drugs better. Use the Medicare Plan Finder tool to compare costs across plans. Look at the total yearly cost-not just the monthly premium. A plan with a $40 premium but $200 monthly drug costs might be worse than a $100 premium plan with $20 drug costs.

Final Tip: Don’t Wait for the Letter

Insurance companies aren’t required to call you. They send letters. But if you’re not checking your formulary, you won’t know the letter came. And if you miss the 60-day window, you might be stuck paying more for months. Check your plan’s formulary now. Do it before your next refill. It takes 5 minutes. It could save you hundreds.