Medicare Part D is the prescription drug side of Medicare, and it is the piece most people understand least. It is not a government-run plan. It is a menu of private plans that follow federal rules, and those rules changed more between 2024 and 2026 than in the program’s first seventeen years.
The single biggest change is a hard annual ceiling on what you pay. For 2026, Medicare.gov puts that ceiling at $2,100 in covered out-of-pocket drug spending. CMS’s CY 2027 Rate Announcement, released April 6, 2026, moves it to $2,400 for next year. Here is how the coverage works, what it actually costs, and when you can reasonably skip a plan.
What Part D Is
Part D is outpatient prescription drug coverage sold by private insurers under contract with Medicare. Medicare.gov’s parts-of-Medicare page describes two ways to get it: a standalone prescription drug plan (a PDP) that sits next to Original Medicare, or drug coverage bundled inside a Medicare Advantage plan (an MA-PD).
You cannot buy Part D from the federal government directly, and there is no national price. Each plan sets its own premium, its own deductible up to the federal maximum, and its own covered-drug list. That list, called a formulary, is where most surprises live, so read how formularies work before you compare premiums.
Part D is one of four parts of the program. If the alphabet is still fuzzy, start with the four parts of Medicare explained.
How the 2026 Benefit Actually Works
Medicare.gov describes three coverage stages for 2026. The old fourth stage, the coverage gap, is gone. There is no longer a donut hole to fall into.
Deductible stage. You pay 100% of the cost of covered drugs until you meet your plan’s deductible. No 2026 plan may set a deductible above $615, and some set $0. Zero-deductible plans are getting rare: KFF’s 2026 analysis found only 4% of standalone drug plan enrollees and 18% of Medicare Advantage drug plan enrollees are in a plan with no drug deductible, down from 15% and 40% respectively in 2025.
Initial coverage stage. Under the standard benefit you pay 25% coinsurance on generics and brand-name drugs until your out-of-pocket spending on covered Part D drugs reaches $2,100. Payments made on your behalf, such as through Extra Help, count toward that total.
Catastrophic stage. Once you cross $2,100, you pay nothing out of pocket for covered Part D drugs for the rest of the calendar year. That is a genuine $0, not 5% coinsurance as it was before 2024.
Two categories sit outside this math entirely. Insulin is capped at $35 for a one-month supply of each covered product, with no deductible applied, per Medicare.gov’s insulin page. Adult vaccines recommended by the Advisory Committee on Immunization Practices, including shingles and RSV, cost $0 with no copay and no deductible. If you are comparing what those cost without coverage, see insulin cash prices and shingles vaccine cost.
Hitting a $615 deductible in January still stings even when the annual total is capped. The Medicare Prescription Payment Plan lets you spread that bill across the calendar year, though it does not lower it.
What It Costs
Figures below are the current CMS and Medicare.gov numbers for 2026, with the 2027 parameters CMS has already announced.
| What you pay | 2026 | 2027 (announced by CMS) |
|---|---|---|
| Average standalone drug plan premium | $36/month | Not yet published |
| Average Part D premium inside a Medicare Advantage plan | $8/month | Not yet published |
| National base beneficiary premium | $38.99 | $41.33 |
| Maximum plan deductible | $615 | $700 |
| Annual out-of-pocket cap on covered drugs | $2,100 | $2,400 |
| Insulin, one-month supply per product | $35 max | $35 max (statutory) |
| ACIP-recommended adult vaccines | $0 | $0 |
| Income surcharge (IRMAA) above $109,000 single / $218,000 joint | $14.50 to $91.00/month | Not yet published |
The premium averages come from KFF’s 2026 Part D analysis, weighted by March 2026 enrollment. The average standalone plan premium fell 7% from $39 in 2025 to $36 in 2026, which KFF credits to the temporary CMS premium stabilization demonstration. That demonstration ends after 2026: CMS’s July 28, 2026 bid fact sheet states it will discontinue the program at the end of CY 2026 and return to traditional market conditions in 2027. Expect standalone premiums to move more freely next year.
The base beneficiary premium is not what you pay. It is the reference number CMS uses for two things: the government subsidy formula and the late enrollment penalty, which runs 1% of it per uncovered month, permanently. CMS set it at $38.99 for 2026 and $41.33 for 2027.
The income surcharge is separate from your plan premium and is paid to Medicare, not the plan. CMS’s November 14, 2025 fact sheet sets the 2026 Part D adjustment amounts at $14.50, $37.50, $60.40, $83.30 and $91.00 a month across five income tiers, affecting roughly 8% of Part D enrollees. If a one-time income event pushed you into a bracket, you can appeal the IRMAA.
Two drug-specific price cuts are now flowing through Part D. CMS’s first negotiation cycle produced Maximum Fair Prices for 10 Part D drugs effective January 1, 2026: Eliquis at $231 for a 30-day supply against a $521 list price, Jardiance at $197, Xarelto at $197, Farxiga at $178.50, Januvia at $113 and Entresto at $295, plus Enbrel, Imbruvica, Stelara and the NovoLog and Fiasp insulins. CMS’s second cycle covers 15 more Part D drugs with prices effective January 1, 2027, including Ozempic, Rybelsus and Wegovy at $274 for a 30-day supply against a $959 list price, Trelegy Ellipta at $175, Xtandi at $7,004 and Linzess at $136. CMS projects $685 million in out-of-pocket savings for enrollees in 2027 under the standard benefit design. Plans must carry these drugs on their formularies.
Who Needs It and Who Should Skip It
Almost everyone on Medicare needs creditable drug coverage from somewhere, because the penalty for going without is permanent. Medicare.gov defines the trigger as 63 or more days in a row without Part D or other creditable coverage after your Initial Enrollment Period ends.
Skip a standalone plan if you already have creditable drug coverage: an employer or union retiree plan, TRICARE, VA pharmacy benefits, or FEHB. Those generally count, and your plan must tell you in writing each year whether its coverage is creditable. Also skip it if you are enrolling in a Medicare Advantage plan that already includes drug coverage, because joining a separate drug plan usually disenrolls you from the Advantage plan.
Buy a plan even if you take nothing when you have no other creditable coverage. A low-premium plan stops the penalty clock and covers you if a prescription appears mid-year, and Medicare.gov gives exactly that advice.
Check Extra Help first if money is tight. Extra Help eliminates the late enrollment penalty going forward and cuts cost sharing sharply, and the related Medicare Savings Programs can pay your Part B premium. For drugs a plan will not cover at all, manufacturer assistance programs are the next stop.
Enrollment windows matter. Per Medicare.gov, your Initial Enrollment Period runs three months before through three months after you get Medicare. Open Enrollment is October 15 to December 7 every year, with coverage starting January 1. Medicare Advantage enrollees get a second window January 1 to March 31. Special Enrollment Periods cover moves, coverage losses and gaining Medicaid or Extra Help.
Part D vs Medicare Advantage Drug Coverage (MA-PD)
Most people with Part D no longer buy it separately. KFF reports that 56% of the 56.3 million Part D enrollees in 2026 get their drug coverage through a Medicare Advantage plan.
| Standalone drug plan (PDP) | Medicare Advantage drug plan (MA-PD) | |
|---|---|---|
| Pairs with | Original Medicare, plus optional Medigap | Nothing else; it is your whole plan |
| Average 2026 drug premium | $36/month | $8/month |
| Enrollees with no drug deductible, 2026 | 4% | 18% |
| Doctor choice | Any provider accepting Medicare | Plan network, usually with prior authorization |
| Medical out-of-pocket cap | None under Original Medicare | $9,250 in network in 2026 |
The $8 average is real but misleading on its own. Advantage plans fund it with rebate dollars that standalone plans cannot use, and the tradeoff is a network and a separate set of medical rules. That is a whole-plan decision, not a drug decision, so weigh it in Medicare Advantage vs Original Medicare rather than on premium alone.
The Bottom Line
Part D in 2026 has a real ceiling for the first time: $2,100, rising to $2,400 in 2027. Below that ceiling, your plan choice still drives everything, because deductibles run from $0 to $615 and formularies decide whether your specific drug is covered at all.
Compare on total annual cost for your actual drug list, not on premium. The step-by-step plan comparison walks through it, and what Part D really costs breaks down the full 2026 numbers.