Introduction: What Is Medicare Part D?
When people search "Medicare Plan D," they almost always mean Medicare Part D, the benefit that helps pay for outpatient prescription drugs. It's not the same as Medigap Plan D, a supplement policy that covers Part A and Part B gaps and does not include drug coverage.
Original Medicare doesn't cover most prescriptions you pick up at a pharmacy. That leaves a gap many new enrollees don't see until the first big pharmacy bill. Part D fills it, either through a standalone plan or through a Medicare Advantage plan with drug coverage.
This guide covers what Part D includes, how formularies and costs work, who can enroll and when, and how to compare plans. Figures here are for 2026. Confirm them on Medicare.gov and in your plan's current documents before you decide.
Key Takeaways
- Part D is optional drug coverage sold by Medicare-approved private insurers.
- You get it through a standalone plan or a Medicare Advantage plan with drug coverage.
- Formularies, tiers, and pharmacy networks vary, so the lowest premium may not mean the lowest yearly cost.
- Enrolling on time, or keeping creditable coverage, helps you avoid a late enrollment penalty.
What Is Medicare Part D and What Does It Cover?
Medicare Part D covers outpatient prescription drugs you fill at a pharmacy. Medicare Part B covers only a limited set of drugs given in an office or outpatient setting, such as certain injected or infused drugs and some oral cancer drugs. Part D picks up many prescriptions Part B doesn't.
Two Ways to Get Part D
- Standalone Prescription Drug Plan (PDP): pairs with Original Medicare.
- Medicare Advantage with drug coverage (MA-PD): bundles medical and drug coverage in one private plan.
Formularies and Tiers
Every plan publishes a formulary, its list of covered drugs. Each drug sits in a tier, and lower tiers generally cost less. The same medication can land in a different tier, or be restricted, on a competing plan.
Plans must cover most drugs in six protected classes:
- Anticonvulsants
- Antidepressants
- Antipsychotics
- Cancer drugs
- HIV/AIDS drugs
- Transplant immunosuppressants
Restrictions to Check
- Prior authorization: the plan must approve the prescription first.
- Step therapy: you try a lower-cost similar drug first.
- Quantity limits: the plan caps how much it covers.
Review these before you enroll or fill a new prescription.
2026 Rules Worth Knowing
- Insulin: no deductible, and monthly cost sharing is capped at the lesser of $35 or a formula tied to negotiated prices.
- Vaccines: ACIP-recommended adult vaccines covered under Part D have $0 cost sharing and no deductible.
- Negotiated prices: the first 10 selected drugs, including Eliquis, Jardiance, Xarelto, and Enbrel, have negotiated prices effective January 1, 2026.
Drug lists, networks, and costs can change every year. Each September, your plan sends an Annual Notice of Change and an Evidence of Coverage. Read both.
How Medicare Part D Costs and Coverage Phases Work
The Main Cost Pieces
- Monthly premium
- Annual deductible (up to $615 in 2026)
- Copayments or coinsurance
- Pharmacy pricing
- Income-related surcharge (IRMAA), if applicable
CMS projects average monthly premiums of $34.50 for standalone plans and $11.50 for the drug portion of MA-PD plans after rebates. These are averages, not quotes.
Coverage Phases in 2026
- Deductible: you pay full cost, up to $615, unless your plan has a lower or no deductible.
- Initial coverage: standard coinsurance is 25% until you reach the annual limit.
- Catastrophic coverage: after you spend $2,100 out of pocket on covered drugs, you pay $0 for the rest of the year.
Premiums don't count toward the $2,100. The old "donut hole" was eliminated starting in 2025.
Income-Related Surcharge
Higher earners pay an added monthly amount. For 2026, it ranges from $0 for individual income of $109,000 or less to $91.00 a month at $500,000 or more.
Spreading Out Costs
The Medicare Prescription Payment Plan lets you spread out-of-pocket drug costs across the remaining months of the year. There are no fees or interest, but it doesn't lower your total. It helps most when big costs hit early.
Why Total Cost Beats Premium
Picture two plans. Plan A charges $10 a month but puts your brand-name drug in a high tier with a $615 deductible. Plan B charges $40 but places it in a lower tier with no deductible.
If you take that drug all year, Plan B can cost far less overall. Run your own list through each plan before deciding.
Who Can Get Medicare Part D and When to Enroll
Eligibility
To enroll in a Medicare Part D plan, you must:
- Have Medicare Part A and/or Part B
- Live in the plan's service area
- Be a U.S. citizen or lawfully present
An MA-PD (Medicare Advantage plan with drug coverage) requires both Parts A and B.
Enrollment Periods
| Period | When | What you can do |
|---|---|---|
| Initial Enrollment Period | 7 months around your 65th birthday | Join your first plan |
| Annual Election Period | Oct 15 - Dec 7 | Join, switch, or drop; starts Jan 1 |
| MA Open Enrollment | Jan 1 - Mar 31 | Those already in MA can make one change |
| Special Enrollment Periods | Varies | Moves, loss of creditable coverage, Medicaid/Extra Help (monthly), institutional residence, plan nonrenewal |
Creditable Coverage and the Penalty
Creditable coverage is drug coverage expected to pay at least as much as standard Medicare drug coverage. Employer, union, retiree, VA, and TRICARE plans may qualify. Your plan's annual notice will say whether the coverage is creditable.
If you go 63 or more consecutive days without Part D or creditable coverage after your initial enrollment period, a penalty may apply. For 2026, it's 1% of $38.99 for each full month without coverage. Keep records of prior coverage.
Check before dropping employer or retiree coverage. Enrolling in Part D can end that coverage for you and your dependents, sometimes including medical benefits.
How to Choose a Medicare Part D Plan
Match your drugs, costs, and pharmacy before you enroll. Work through these steps in order.
- Build a medication list. Note each drug's name, dosage, frequency, quantity, prescriber, and preferred pharmacy.
- Check each formulary. Look at tier, prior authorization, step therapy, quantity limits, and covered alternatives.
- Compare yearly cost. Add premiums, deductible, copays or coinsurance, and mail-order options. Use Medicare's Plan Finder and read the Evidence of Coverage.
- Verify your pharmacy. Preferred network pharmacies may charge less than standard network ones. Some plans cover prescriptions only at network pharmacies.
- Weigh PDP versus MA-PD. An MA-PD adds a medical network, provider access, and cost sharing to the decision. Its medical out-of-pocket limit is separate from the Part D limit. Joining a standalone PDP while enrolled in Medicare Advantage generally returns you to Original Medicare.
Muneris Benefits, an independent agency in Roanoke and Narrows, Virginia, offers personalized Medicare guidance to help people compare options and understand plan details. Confirm current availability and costs in the official plan materials.
Medicare Part D With Other Coverage and Help Paying for Drugs
Medigap and Other Coverage
Medigap policies sold after 2005 don't include drug coverage. Pair one with a standalone Part D plan. That pairing is separate from "Medigap Plan D."
Here's how Part D works with other common coverage:
- FEHB: keep it alongside Part D, but you can't drop its drug coverage without dropping its medical coverage.
- VA: keep both, but one prescription can't be paid by both.
- TRICARE: you generally don't need a separate PDP.
- Medicaid: full Medicaid brings automatic Extra Help.
If Prescriptions Are Unaffordable
- Check Extra Help. The 2026 income limits are $23,940 (individual) and $32,460 (married couple).
- Ask about the Medicare Prescription Payment Plan.
- Ask your prescriber about lower-cost formulary alternatives.
- Request a formulary or tiering exception. Decisions arrive within 72 hours, or 24 hours if expedited.
- Call your State Health Insurance Assistance Program (SHIP) at 1-877-839-2675 for unbiased help.
Frequently Asked Questions
What is Medicare Part D and how does it work?
Part D is optional outpatient drug coverage from Medicare-approved private insurers. You get it through a standalone plan alongside Original Medicare or through a Medicare Advantage plan that includes drugs.
Do I need Medicare Part D, and is it worth it?
It's voluntary, but it protects you from high drug costs and from a late enrollment penalty if you have no creditable coverage. Even if you take few drugs now, future needs are hard to predict.
What is the average monthly premium for Medicare Part D in 2026?
CMS projects $34.50 for standalone plans and $11.50 for the drug portion of Medicare Advantage plans that include drugs (MA-PDs). Your actual premium depends on plan, location, income, and drugs.
How do I choose the best Medicare Part D plan?
Compare your full medication list against each plan's formulary, tiers, pharmacy network, restrictions, and total yearly cost. Don't pick by premium alone.
What are the requirements to be eligible for Medicare Part D?
You need Part A and/or Part B, must live in the plan's service area, and must enroll during a valid enrollment period.
Can I have Part D if I also have private insurance or Medigap?
Yes, depending on the other coverage. Medigap doesn't cover outpatient drugs, so it pairs with a standalone plan. Verify creditable coverage before enrolling or dropping anything.
