Medicare Part D is a voluntary prescription drug benefit offered through private insurance companies that contract with the federal government. It helps pay for outpatient medications — both brand-name and generic — for anyone enrolled in Medicare. Under the Inflation Reduction Act of 2022, Part D now caps yearly out-of-pocket drug costs at $2,100 in 2026, a change that protects roughly 11 million enrollees from runaway prescription spending.
About 54.8 million of the 68.8 million total Medicare beneficiaries are enrolled in Part D plans as of 2025. Yet an estimated 11% of people with Medicare still lack creditable drug coverage — and many of them don’t realize they’re racking up lifetime late enrollment penalties for every month they delay.
Here’s what you’ll learn in this article:
- 💊 How Medicare Part D’s three coverage phases work and what you’ll pay during each one
- 💰 How the $2,100 annual out-of-pocket cap saves you money on expensive prescriptions
- 📋 How to choose between a stand-alone Part D plan and Medicare Advantage drug coverage
- ⚠️ How the late enrollment penalty is calculated and how to avoid it
- 🛡️ How the Medicare Prescription Payment Plan lets you spread costs into monthly payments
What Exactly Is Medicare Part D?
Medicare Part D is the outpatient prescription drug benefit within the Medicare program. It was established in 2003 under the Medicare Modernization Act and first became available in January 2006. Private insurance companies — not the government — run Part D plans, but they must follow rules set by the Centers for Medicare & Medicaid Services (CMS).
Part D coverage comes in two forms. You can get a stand-alone Prescription Drug Plan (PDP) that adds drug coverage to Original Medicare (Parts A and B). You can also get drug coverage bundled into a Medicare Advantage Prescription Drug Plan (MA-PD), which wraps hospital, medical, and drug benefits into one plan.
In 2026, beneficiaries in each state can choose from 8 to 12 stand-alone PDPs — a 22% decrease from 2025 — plus many Medicare Advantage drug plans offered at the county level. Even with fewer plan options, the federal government requires every Part D plan to meet minimum coverage standards.
Who Can Enroll in Medicare Part D?
To join a Part D plan, you must have Medicare Part A or Part B, live within the plan’s service area, and be a U.S. citizen or lawfully present in the United States. You also need to complete an enrollment request during a valid election period.
The Initial Enrollment Period (IEP)
The best time to sign up for Part D is during your Initial Enrollment Period. This is the same 7-month window you get when you first become eligible for Medicare — it starts 3 months before you turn 65, includes your birthday month, and continues for 3 months after. If you miss this window and don’t have other creditable prescription drug coverage, a late enrollment penalty kicks in.
Fall Open Enrollment (October 15 – December 7)
During Fall Open Enrollment, you can freely add, drop, or switch Part D plans — whether stand-alone or through Medicare Advantage. Changes made during this period take effect on January 1 of the following year.
Medicare Advantage Open Enrollment (January 1 – March 31)
If you’re already in a Medicare Advantage plan, you can make one change during this window. You can switch between MA plans with drug coverage or move back to Original Medicare and add a stand-alone PDP.
Special Enrollment Periods (SEPs)
You may qualify for a Special Enrollment Period if you experience certain life events — such as moving out of your plan’s service area, losing your current drug coverage, or qualifying for Extra Help (the Low-Income Subsidy). SEPs let you modify your Part D coverage outside the normal enrollment windows.
The Three Phases of Part D Coverage in 2026
Part D drug costs don’t work like a flat monthly bill. Your out-of-pocket costs change as you move through three coverage phases over the calendar year. The Inflation Reduction Act simplified this structure starting in 2025 by eliminating the old “donut hole” coverage gap.
| Coverage Phase | What You Pay |
|---|---|
| Deductible Phase | 100% of drug costs until you reach your plan’s deductible (up to $615 in 2026) |
| Initial Coverage Phase | 25% coinsurance (your plan pays 75%) until your out-of-pocket spending reaches $2,100 |
| Catastrophic Coverage Phase | $0 — your plan pays 100% of covered drug costs for the rest of the year |
Phase 1: The Deductible
You pay the full cost of your prescriptions until you meet your plan’s annual deductible. The maximum deductible in 2026 is $615, but some plans charge a lower deductible or no deductible at all. Plans may also waive the deductible for certain lower-tier drugs like preferred generics.
Phase 2: Initial Coverage
After you meet the deductible, your plan starts sharing costs with you. You typically pay 25% coinsurance — or a flat copay depending on your plan’s tier structure — while the plan covers the remaining 75%. You stay in this phase until your total out-of-pocket spending hits $2,100, which includes the deductible you already paid.
Phase 3: Catastrophic Coverage
Once your out-of-pocket costs reach $2,100, you enter catastrophic coverage and pay nothing for covered drugs for the rest of the year. Before the Inflation Reduction Act, beneficiaries still owed 5% coinsurance after reaching the catastrophic level — which could mean thousands of dollars a year for people on expensive medications. That 5% cost-sharing was eliminated in 2024, and the hard dollar cap was added in 2025.
How Drug Formularies and Tiers Affect Your Costs
Every Part D plan maintains a formulary — a list of the prescription drugs it covers. Each plan organizes its formulary into cost-sharing “tiers,” and the tier your drug falls into determines how much you pay.
| Drug Tier | What It Covers |
|---|---|
| Tier 1 — Preferred Generic | Lowest-cost generic drugs; often $0 or minimal copay |
| Tier 2 — Non-Preferred Generic | Higher-cost generic drugs; low copay |
| Tier 3 — Preferred Brand | Lower-cost brand-name drugs; moderate copay or coinsurance |
| Tier 4 — Non-Preferred Brand | Higher-cost brand-name drugs; higher coinsurance |
| Tier 5 — Specialty | Very high-cost drugs (often $1,000+/month); highest coinsurance |
Plans must cover at least two chemically distinct drugs in the most commonly prescribed categories. They must also cover all drugs in six protected classes: cancer drugs, HIV/AIDS drugs, antidepressants, antipsychotics, anticonvulsants, and immunosuppressants for organ transplants.
If a drug you need isn’t on your plan’s formulary, you can request an exception from the plan. Your prescribing doctor must submit a statement explaining why no alternative on the formulary will work. You can also request a tiering exception to pay a lower cost-sharing amount for a drug on a higher tier.
How Medicare Is Negotiating Drug Prices Under the IRA
The Inflation Reduction Act gave Medicare the authority — for the first time — to directly negotiate prices on certain expensive brand-name drugs. The first round of negotiations focused on 10 high-cost Part D drugs, and those negotiated prices took effect on January 1, 2026. These medications treat serious chronic illnesses like diabetes, heart failure, cancer, blood clots, autoimmune conditions, and chronic kidney disease.
Additional drugs are being selected for negotiation each year, with prices scheduled to take effect in subsequent years. All Part D plans are required to cover all dosage forms and strengths of any drug selected for negotiation. Drug manufacturers that raise prices faster than the rate of inflation must also pay rebates back to the federal government.
Real-World Example: Maria Hits the Out-of-Pocket Cap
Maria, age 68, takes a brand-name cancer drug that costs $1,800 per month at retail. She enrolled in a stand-alone PDP with a $615 deductible and standard 25% coinsurance.
| Month | What Happens | Maria’s Out-of-Pocket Cost |
|---|---|---|
| January | Maria pays her full deductible plus 25% of remaining costs | $615 (deductible) + $296.25 (25% of $1,185) = $911.25 |
| February | Maria pays 25% coinsurance on her $1,800 prescription | $450 |
| March | Maria’s cumulative out-of-pocket hits $2,100 partway through the month — she enters catastrophic coverage | $738.75 (partial month) then $0 after reaching the cap |
| April – December | Catastrophic phase — plan pays 100% | $0 per month |
Maria’s total out-of-pocket drug spending for the year: $2,100. Before the Inflation Reduction Act, Maria could have paid over $10,000 annually. The $2,100 cap saved her thousands.
Real-World Example: James Uses Only Generic Medications
James, age 72, takes three generic medications: a blood pressure pill, a cholesterol drug, and a diabetes medication. His combined monthly drug cost is $45. He chose a plan with no deductible for Tier 1 generics and a $5 copay per prescription.
| Month | What Happens | James’s Out-of-Pocket Cost |
|---|---|---|
| January – December | James pays $5 copay × 3 drugs per month | $15/month |
| Full Year | James never leaves the Initial Coverage Phase | $180 total |
James never comes close to the $2,100 cap because his drug costs are low. For beneficiaries like James who take only generics, choosing a plan with low Tier 1 copays and no deductible makes the biggest difference.
Real-World Example: Susan Needs a Specialty Drug Mid-Year
Susan, age 66, is diagnosed with rheumatoid arthritis in April and prescribed a Tier 5 specialty biologic costing $3,500 per month. She has a plan with a $615 deductible and had paid only $100 in out-of-pocket costs from January through March.
| Month | What Happens | Susan’s Out-of-Pocket Cost |
|---|---|---|
| January – March | Susan uses a low-cost generic; $100 total out-of-pocket | $100 |
| April | Susan fills her new specialty drug. She pays remaining $515 deductible + 25% coinsurance. She hits the $2,100 cap mid-month. | $2,000 (capped) |
| May – December | Catastrophic phase — $0 out of pocket | $0 |
Susan’s total for the year: $2,100. Without the cap, Susan would have owed more than $8,000 in coinsurance on a $3,500-per-month drug.
The Medicare Prescription Payment Plan: Spreading Costs Monthly
Even with a $2,100 cap, paying hundreds of dollars upfront in January can be difficult. That’s why the Medicare Prescription Payment Plan was created under the Inflation Reduction Act. All Part D plans are required to offer this option.
The Payment Plan lets you spread your out-of-pocket prescription drug costs into capped monthly installments instead of paying everything at the pharmacy counter. Your plan calculates your estimated drug costs for the year and divides them across remaining months.
Here’s how the math works for someone with $500/month in drug costs who enrolls in January:
| Month | New Drug Costs | Monthly Payment |
|---|---|---|
| January | $500 | $175 (calculated using “maximum possible payment” method for the first month) |
| February | $500 | $79.55 |
| March | $500 | $132.05 |
| April | $500 | $190.38 (reaches $2,100 cap this month) |
| May – December | $0 new OOP costs | Remaining balance spread across final months |
The key benefit: you never face a massive bill in a single month. The plan smooths your costs so you can budget predictably. You can opt in or out of the Payment Plan at any time during the year.
The Late Enrollment Penalty: A Lifetime Surcharge
If you go 63 days or more without Medicare drug coverage or other creditable prescription drug coverage after your Initial Enrollment Period ends, you will pay a permanent late enrollment penalty. This penalty is added to your monthly Part D premium for as long as you have Part D coverage.
How the Penalty Is Calculated
The penalty equals 1% of the national base beneficiary premium multiplied by the number of months you went without coverage, rounded to the nearest $0.10. For 2026, the national base beneficiary premium is $38.99.
Example: Frank became eligible for Medicare in May 2022 but didn’t enroll in Part D until December 2025. He had 43 months without creditable drug coverage.
| Calculation Step | Amount |
|---|---|
| National base beneficiary premium (2026) | $38.99 |
| Penalty rate: 1% × 43 months = 43% | 43% of $38.99 = $16.76 |
| Rounded to nearest $0.10 | $16.80/month |
Frank now pays an extra $16.80 every month on top of his regular Part D premium — and this penalty never goes away. Because the base premium changes each year, the dollar amount of Frank’s penalty will be recalculated annually, but the 43% rate stays with him for life.
When You Won’t Face the Penalty
You are exempt from the late enrollment penalty if you:
- Qualify for Extra Help (the Part D Low-Income Subsidy)
- Had creditable coverage through an employer, union, the VA, TRICARE, or a spouse’s plan
- Were enrolled in a Medicare Savings Program (QMB, SLMB, or QI)
Stand-Alone PDP vs. Medicare Advantage Drug Plan
Choosing between a stand-alone PDP and an MA-PD is one of the biggest decisions you’ll make during enrollment. Each option has trade-offs.
| Feature | Stand-Alone PDP | Medicare Advantage Drug Plan (MA-PD) |
|---|---|---|
| Works with | Original Medicare (Parts A & B) | Replaces Original Medicare entirely |
| Average monthly premium | $39 (2025 average) | $7 for drug portion (many are $0) |
| Doctor network | Any doctor who accepts Medicare | Must use plan’s provider network |
| Out-of-pocket cap on drugs | $2,100 (2026) | $2,100 (2026) |
| Extra benefits | None (drug coverage only) | May include dental, vision, hearing, fitness |
| Flexibility | Choose any Medigap supplement | Cannot use Medigap with MA plans |
About 58% of Part D enrollees are now in MA-PDs, driven largely by the appeal of low or zero premiums for drug coverage. However, MA plans restrict your choice of doctors and hospitals to an in-network list, which can be a serious drawback if you want freedom to see any provider.
The Low-Income Subsidy (Extra Help)
Medicare’s Extra Help program — also called the Low-Income Subsidy (LIS) — provides premium and cost-sharing assistance to Part D enrollees with limited income and assets. As of May 2025, 13.9 million Part D enrollees receive this assistance.
To qualify for full Extra Help benefits, your income must be below 150% of the federal poverty level ($23,475 for individuals / $31,725 for married couples in 2025), and your assets must not exceed $17,600 for individuals / $35,130 for couples. People who qualify pay no deductible, modest copays for prescriptions, and no premium if they enroll in a benchmark plan.
You can apply for Extra Help through the Social Security Administration or through your state Medicaid office. Beneficiaries who are dual-eligible for both Medicare and Medicaid, or who receive Supplemental Security Income (SSI), are automatically enrolled.
Pros and Cons of Medicare Part D
| Pros | Cons |
|---|---|
| $2,100 annual out-of-pocket cap protects against catastrophic drug costs | Monthly premiums add to your Medicare expenses even if you use few drugs |
| Formularies must cover drugs in six protected classes and negotiated drugs | Your specific drug may not be covered on every plan’s formulary |
| Extra Help program offers near-free coverage for low-income beneficiaries | Late enrollment penalty is permanent if you delay without creditable coverage |
| Medicare Prescription Payment Plan lets you spread costs into monthly payments | Plan formularies change yearly, so a drug covered this year may not be covered next year |
| Drug price negotiation under the IRA is lowering costs on expensive brand-name drugs | Stand-alone PDP premiums are rising, with some plans increasing by $50 or more per month in 2026 |
How to Enroll in Medicare Part D: Step-by-Step
The easiest way to enroll is through the Medicare Plan Finder tool on Medicare.gov. Here’s how:
- Go to Medicare.gov and click “Find Plans Now” under the Find Health & Drug Plans section.
- Log in to your Medicare account or enter your ZIP code and select your county.
- Select the plan type you want — choose “Medicare Drug Plan (Part D)” for prescription drug coverage.
- Enter your pharmacy — type in the name or address of the pharmacy you prefer to use. You can add multiple pharmacies.
- Add your prescriptions — type each drug name into the search bar, then specify the dosage, quantity, and frequency. Click “Add to My Drug List” for each one.
- Review plan results — Medicare will show you plans ranked by estimated annual cost, including premiums, deductibles, copays, and star ratings.
- Click “Enroll” on the plan you choose — you’ll see a pop-up asking for your Medicare number, effective dates, and information about any current health coverage.
- Complete and submit the application — review every section, confirm your enrollment period, and sign the plan agreement electronically.
You can also enroll by calling 1-800-MEDICARE (1-800-633-4227), calling the insurance company directly, visiting the insurer’s website, or mailing a paper application.
Part D Spending and Who Pays for It
Medicare’s actuaries estimate that spending on Part D benefits will total $141 billion in 2026, which represents 11% of all Medicare benefit spending.
| Funding Source | Share of Part D Costs |
|---|---|
| Federal government contributions | 75% |
| Beneficiary premiums | 13% |
| State contributions | 12% |
The Inflation Reduction Act shifted more financial responsibility to Part D plans and drug manufacturers for catastrophic-level drug costs. Medicare’s reinsurance payments — which once covered 80% of catastrophic spending — now cover just 20% for brand-name drugs and 40% for generics. This means insurers and drugmakers are paying a much bigger share, which is one reason premiums have been rising.
Mistakes to Avoid With Medicare Part D
Skipping Part D because you’re healthy right now. Even if you don’t take any medications today, going without creditable drug coverage triggers the late enrollment penalty — 1% of the base premium for every single month you delay. A 5-year gap could cost you an extra $23/month for life.
Assuming your drugs are covered without checking. Formularies vary widely between plans. A drug covered by one plan may be excluded or placed on a higher tier by another. Always use the Medicare Plan Finder to search your specific medications before enrolling.
Not reviewing your plan every year. Part D plans can change their formulary, copay amounts, and pharmacy networks each January. A plan that was perfect last year may drop your drug, raise your copay, or remove your preferred pharmacy this year.
Ignoring the Medicare Prescription Payment Plan. Many beneficiaries don’t know they can spread their out-of-pocket costs into monthly installments. If you take expensive drugs and face a large bill in January, opting into this plan prevents financial strain early in the year.
Not applying for Extra Help when eligible. Millions of low-income Medicare beneficiaries qualify for premium and cost-sharing assistance but never apply. If your income is below 150% of the federal poverty level, you could pay zero premium and only small copays.
Do’s and Don’ts of Medicare Part D
| Do’s | Don’ts |
|---|---|
| Do enroll during your IEP to avoid the late penalty | Don’t assume your employer coverage automatically qualifies as “creditable” — verify it in writing |
| Do use the Medicare Plan Finder to compare plans side by side using your actual drug list | Don’t pick a plan based only on premium — a cheap plan may have high copays for your drugs |
| Do check if your drugs are in the plan’s formulary and which tier they’re on | Don’t forget to add your preferred pharmacy when comparing plans — costs differ between in-network and out-of-network pharmacies |
| Do review your Part D coverage every fall during Open Enrollment (Oct 15 – Dec 7) | Don’t wait until you’re sick to sign up — the penalty compounds for every uncovered month |
| Do ask your doctor about generic alternatives to lower your tier costs | Don’t ignore letters from your plan about formulary changes — your drug could be dropped or moved to a higher tier |
FAQs
Is Medicare Part D mandatory?
No. Part D is voluntary, but if you delay enrollment without creditable drug coverage, you’ll pay a permanent late penalty added to your monthly premium for life.
Does Medicare Part D cover insulin?
Yes. All Part D plans cap insulin costs at $35 per month per covered insulin product, thanks to the Inflation Reduction Act.
Is there a deductible for Medicare Part D?
Yes. The maximum deductible in 2026 is $615, but many plans charge less or waive the deductible for lower-tier generics.
Can I switch Part D plans during the year?
No. You can only switch during Fall Open Enrollment (Oct 15 – Dec 7) or during a Special Enrollment Period if you qualify for one.
Does the $2,100 cap include my premium?
No. The cap only counts your deductible, copays, and coinsurance. Your monthly premium does not count toward the out-of-pocket limit.
Do Part D plans cover vaccines?
Yes. Part D must cover all commercially available adult vaccines recommended by the Advisory Committee on Immunization Practices at $0 cost to you.
Can I have Part D and VA drug coverage at the same time?
Yes. You can have both, but VA coverage counts as creditable coverage, so you won’t face a late enrollment penalty if you delay Part D while using VA benefits.
Does Medicare Part D cover over-the-counter drugs?
No. Part D only covers outpatient prescription drugs prescribed by a doctor. Some Medicare Advantage plans may offer separate OTC allowances.
What happens if my drug isn’t on the formulary?
No, it won’t be covered automatically. You can request a formulary exception with a supporting statement from your doctor explaining medical necessity.
Is the late enrollment penalty permanent?
Yes. The penalty lasts for as long as you have Part D coverage, even if you switch plans. It is recalculated each year based on the current base premium.
Related reading
- Can Insurance Reimburse You for a Medication? (w/Examples) + FAQs
- When Can Seniors Change Medicare Plans? (w/Examples) + FAQs
- How Do Medicare Supplement Plans Work (w/Examples) + FAQs
- When Should You Sign Up for Medicare Part B? (w/Examples) + FAQs
- Should I Enroll in Medicare Part D? (w/Examples) + FAQs
- Should I Get Medicare Part C or D? (w/Examples) + FAQs
- Is Nationwide Long-Term Care Insurance Worth It? (w/Examples) + FAQs