Catastrophic coverage is the final phase of Medicare Part D’s benefit structure, designed to protect you from unlimited prescription drug costs. Once your out-of-pocket spending hits a set threshold during the calendar year, you enter this phase and pay nothing for covered medications for the rest of that year. Before recent legislative changes, this phase still required you to pay 5% of drug costs with no upper limit, which could mean thousands of dollars for people on expensive specialty drugs. That changed significantly in 2024 and 2025.
How Part D’s Benefit Phases Work
Medicare Part D is structured in stages, and you move through them based on how much you and your plan spend on drugs over the course of a year. The first stage is the deductible, where you pay the full cost of your medications up to a set amount. Next comes the initial coverage period, where you and your plan share costs through copays or coinsurance. After that is the coverage gap (sometimes called the “donut hole”), where your cost-sharing percentage historically increased. Finally, once your cumulative out-of-pocket spending crosses a specific dollar threshold, you enter catastrophic coverage.
The key concept connecting all these phases is something called True Out-of-Pocket costs, or TrOOP. This is the running total Medicare uses to determine when you’ve spent enough to qualify for catastrophic coverage. Your TrOOP includes what you pay toward your deductible, your copays and coinsurance during the initial coverage period, anything you pay during the coverage gap, and manufacturer discounts on brand-name drugs. Notably, your monthly premium does not count toward TrOOP.
What Changed in 2024
The Inflation Reduction Act eliminated the 5% coinsurance that beneficiaries previously owed during the catastrophic phase. Before this change, there was no cap on what you could spend. Someone taking a specialty medication costing $10,000 a month would still owe $500 per month even after reaching catastrophic coverage, and that cost continued indefinitely for the rest of the year. This was one of the most criticized features of Part D’s original design.
In 2024, the catastrophic threshold was set at $8,000 in TrOOP spending. Because manufacturer discounts on brand-name drugs counted toward that total, enrollees taking only brand-name drugs reached the threshold after spending roughly $3,300 out of their own pockets. Once there, they owed nothing more for covered prescriptions for the remainder of the year.
The $2,000 Cap Starting in 2025
The most dramatic shift arrived in 2025. The Inflation Reduction Act lowered the out-of-pocket threshold for entering catastrophic coverage to $2,000. This effectively creates a hard annual cap: once you’ve spent $2,000 out of pocket on covered Part D drugs in a calendar year, your cost-sharing drops to zero for the rest of that year. The $2,000 cap will be adjusted for inflation in future years.
This is a significant departure from how Part D worked for nearly two decades. Before the Inflation Reduction Act, there was no maximum limit on what enrollees could spend. People with conditions requiring expensive medications, such as cancer, multiple sclerosis, or rheumatoid arthritis, could face annual drug costs well into five figures. The new cap means no Medicare Part D enrollee will pay more than $2,000 per year for covered prescriptions, regardless of how expensive their medications are.
What Counts Toward the $2,000 Threshold
Not every dollar you spend on prescriptions brings you closer to catastrophic coverage. The expenses that count toward TrOOP are:
- Your annual deductible, if your plan charges one
- Copays and coinsurance you pay during the initial coverage period
- Payments during the coverage gap for covered drugs
- Manufacturer discounts on brand-name drugs provided through the Medicare discount program
Payments that do not count include your monthly Part D premium, costs for drugs not on your plan’s formulary, and any spending covered by other insurance or assistance programs (with some exceptions). The manufacturer discount piece is worth understanding because it can push you through the phases faster than your actual wallet spending alone would suggest. If a brand-name drug has a significant manufacturer discount applied during the coverage gap, that discount amount gets added to your TrOOP total even though you didn’t pay it yourself.
How Costs Are Split Behind the Scenes
Once you reach catastrophic coverage, you owe nothing, but the drugs still get paid for. The cost is split between the federal government and your Part D plan. Before the Inflation Reduction Act, the federal government covered about 80% of drug costs in the catastrophic phase, the plan covered roughly 15%, and you paid the remaining 5%. Now that your share has been eliminated, the federal government and drug plans absorb the full cost. Drug manufacturers also contribute through required discounts on brand-name medications.
This restructuring shifted significant financial responsibility onto plans and manufacturers, which is one reason the change was phased in over multiple years rather than implemented all at once.
Who Benefits Most
The people who see the biggest savings from catastrophic coverage changes are those with high drug costs, particularly enrollees taking specialty medications, multiple brand-name drugs, or drugs for chronic conditions that require ongoing treatment. Before the $2,000 cap, it was not unusual for someone on a specialty biologic to spend $5,000 to $10,000 or more per year on prescriptions even with Part D coverage.
If your annual drug costs are modest, say a few generic medications totaling a few hundred dollars per year, you may never reach the catastrophic phase at all. The benefit phases are designed so that most enrollees stay within the deductible and initial coverage periods. Catastrophic coverage primarily matters for the roughly 1.5 million enrollees each year whose drug spending is high enough to push through the earlier phases.
One practical detail worth knowing: Part D plans now offer the option to spread your out-of-pocket costs across the year in monthly installments rather than paying large amounts upfront when you fill expensive prescriptions early in the year. This doesn’t change the $2,000 cap, but it can make the payments more manageable if you’d otherwise face a large bill in January or February.