7 min read · Last updated August 31, 2026
- A specialty-tier drug’s coinsurance percentage, not the deductible, usually decides your real annual cost. The most recent federal survey to measure this put the national average specialty-tier coinsurance at 27.9% in 2020.
- The 2026 out-of-pocket maximum is $10,600 for an individual and $21,200 for a family, per HealthCare.gov. Under a percentage-based specialty tier, that ceiling is often the real number you’ll pay for the year, not a worst-case scenario.
- Find your specific drug’s tier on the plan’s actual formulary document, usually a separate 50-to-100-page PDF, before you compare premiums. The plan comparison chart at open enrollment almost never lists individual drugs by name.
- A flat-dollar copay on the specialty tier can save $9,880 a year over a percentage-based coinsurance design (worked example inside), even when that plan’s deductible and premium both run higher.
In this article
- Why the deductible is the wrong first number
- Find the drug before you compare the plans
- The math that flips the answer
- What to do before enrollment closes
Priya was choosing between two employer health plans during open enrollment. Plan A had a $500 deductible and a lower monthly premium. Plan B had a $1,900 deductible, a higher premium, and looked like the worse deal on every comparison chart her HR portal generated. Her monthly biologic, priced at $4,000 a fill, sat on Plan A’s specialty tier at 30% coinsurance. By month nine, she had paid more toward that one drug than the entire deductible gap between the two plans, several times over.
Why the deductible is the wrong first number
Every open-enrollment comparison tool leads with the deductible because it’s the easiest number to display side by side. For a household with no ongoing prescription need, that’s a reasonable place to start. It falls apart the moment one person in the household takes a drug that lands on the plan’s specialty tier, because a percentage-based coinsurance can turn a $4,000 monthly fill into a four-figure monthly bill that keeps arriving until you hit the plan’s out-of-pocket maximum. For 2026, that ceiling is $10,600 for an individual and $21,200 for a family, according to HealthCare.gov’s own glossary. Under a coinsurance design, that ceiling isn’t a worst-case number. For someone on an expensive specialty drug, it’s frequently the number you’ll actually pay.
The Patient Advocate Foundation’s guide to drug tiers explains the four-tier structure clearly, generic to specialty, and warns readers to watch for plans that charge a co-pay percentage on high-level, expensive drugs, because that cost is often unaffordable and can leave you with an outsized out-of-pocket bill. What it doesn’t do, and what almost nothing written for consumers does, including our own breakdown of out-of-pocket maximums, is put a number on that warning. The most recent federal data that does: the Agency for Healthcare Research and Quality (AHRQ), via its Medical Expenditure Panel Survey Insurance Component, measured the national average specialty-tier coinsurance at 27.9% in 2020, the most recent year this figure was published in that series. Plans commonly run higher, up to 50% on some designs. That is the number that should be driving your plan choice, not the deductible.
Find the drug before you compare the plans
The plan comparison chart your employer hands out at open enrollment almost never lists individual drugs. To find out what tier your specific drug sits on, and what that tier actually costs, you need the plan’s formulary document, not its Summary of Benefits and Coverage. The formulary is usually a separate PDF, often 50 to 100 pages, searchable by drug name, and it’s the only document that will tell you the tier number and the coinsurance percentage or copay amount tied to it.
Search the formulary for your drug by name before enrollment closes, not after. If it isn’t listed at all, or if it’s listed with a prior-authorization or step-therapy requirement, the Patient Advocate Foundation’s guide above lists three grounds for a formulary exception request: the drug isn’t on the formulary but is your best option, it requires a restriction your prescriber can argue against, or it’s covered but you want access to a higher-coverage tier. File that request during enrollment if you need to, not after your first denied fill. If the drug isn’t specialty-tier at all but its everyday cost is still high, our prescription cost order of operations covers the generic, discount-card, and copay-card sequence that applies regardless of which plan you pick.
The math that flips the answer
Here’s the comparison, worked through with Priya’s numbers. Both plans cover the same $4,000-a-month biologic; the difference is entirely in how each plan’s specialty tier is structured.
| Factor | Plan A | Plan B |
|---|---|---|
| Deductible | $500 | $1,900 |
| Specialty tier cost-share | 30% coinsurance | Flat $60 copay per fill |
| Monthly cost for the $4,000 drug | $1,200 (until the out-of-pocket max caps it) | $60 |
| Annual out-of-pocket for this drug | $10,600 (hits the individual out-of-pocket max around month 9) | $720 (12 x $60) |
| Difference | Plan B costs $9,880 less for this one drug over the year | |
| Best for | Households with no ongoing specialty prescription | Anyone on a specialty-tier drug, even with a higher deductible and premium |
Plan A’s coinsurance charges 30% of $4,000 every month, $1,200, until the year’s total cost-sharing reaches the $10,600 out-of-pocket max, which happens around the ninth month. From that point the plan pays 100%, but Priya has already paid the full $10,600 to get there. Plan B’s flat $60 copay per fill never scales with the drug’s price at all: 12 months at $60 comes to $720 for the year. The $1,400 deductible gap that made Plan A look cheaper on the comparison chart is a fraction of the $9,880 this one drug cost Priya over the year.
What to do before enrollment closes
Three steps, in order. First, get the actual formulary document for every plan you’re considering, not the marketing comparison chart. Second, find your specific drug and note whether its tier uses a flat copay or a percentage coinsurance; the structure matters more than the number attached to a low-usage tier. Third, if it’s a coinsurance design, multiply the percentage against your drug’s monthly cost and compare that total against the out-of-pocket maximum, because that calculation, not the deductible, is what will actually leave your bank account over the year.
Frequently asked questions
How do I find my plan’s formulary before I enroll? Ask your HR or benefits portal for the “formulary” or “drug list” document by name, not the plan comparison chart. If you can’t find it there, call the insurance carrier’s member services line listed on the plan summary and ask them to email or link you the current formulary PDF for the specific plan you’re considering.
What if my drug isn’t listed on either plan’s formulary at all? Ask your prescriber’s office to file a formulary exception request during your enrollment window. The Patient Advocate Foundation notes this applies when a drug isn’t covered but is your best clinical option, when it requires a restriction you want waived, or when you want access to a better coverage tier than the one it’s currently assigned.
Is a flat copay always better than a percentage coinsurance for specialty drugs? For an expensive drug, almost always, because a flat copay doesn’t scale with the drug’s price the way coinsurance does. The exception is a very cheap specialty-tier drug, where a high flat copay could occasionally exceed what a low coinsurance percentage would charge. Check both math paths for your specific drug’s price.
Does the out-of-pocket maximum include my premium payments? No. The out-of-pocket maximum only counts deductibles, copays, and coinsurance for covered care. Monthly premiums are a separate cost that never counts toward that $10,600 or $21,200 ceiling, no matter how much you pay in premiums over the year.
Can I switch plans mid-year if I discover my drug’s tier costs more than I expected? Generally no, outside of a qualifying life event that triggers a special enrollment period. This is exactly why finding the formulary and running this math during open enrollment, before you’re locked into a plan year, matters more than almost any other step in the decision.