Medicare Part D in Washington

What Is Medicare Part D?

Medicare Part D is the federal program that provides prescription drug coverage to anyone enrolled in Medicare, including beneficiaries in Washington. Established under the Medicare Modernization Act of 2003, Part D has been delivering coverage since January 2006. Unlike Parts A and B, which are administered directly by the federal government, Part D plans are offered by private insurance companies approved by Medicare — and the plans available to Washington residents vary by county and zip code.

You can get Part D coverage in two ways: through a standalone Prescription Drug Plan (PDP) that pairs with Original Medicare, or through a Medicare Advantage plan that includes drug coverage (sometimes called an MA-PD). Either way, the program is designed to help reduce out-of-pocket costs for the medications you need.

What Does Part D Cover in Washington?

Part D plans in WA cover a wide range of prescription medications, though the specific drugs included vary by plan. Every Part D plan must cover at least two drugs in each therapeutic category and class, and all plans are required to cover substantially all drugs in six protected classes, including cancer medications, antidepressants, and antipsychotics.

Beyond standard prescriptions, Part D also covers:

• Vaccines — including COVID-19, flu, shingles, hepatitis B, and other commercially available vaccines
• Insulin — as of the Inflation Reduction Act, insulin is capped at $35 per month under Part D
• Biosimilar drugs — biological products approved as biosimilars to reference products

Each plan maintains a formulary (a list of covered drugs) organized into tiers, with each tier having different cost-sharing amounts. For a deeper look at what is and isn't included, see our guide on Medicare Part D coverage. You can also review what Medicare covers overall to understand how Part D fits into the bigger picture.

How Much Does Part D Cost in Washington?

Part D costs in Washington break down into several components, and the exact amounts depend on which plan you choose:

• Monthly premium — The national average Part D premium is approximately $35 per month in 2026, though individual plans available to WA residents range from under $10 to over $100 depending on coverage level
• Annual deductible — The maximum Part D deductible for 2026 is $590. Some plans in Washington have lower deductibles or none at all
• Copays and coinsurance — After meeting your deductible, you pay a copay (flat fee) or coinsurance (percentage) for each prescription, depending on the drug's formulary tier
• The donut hole — Part D historically had a coverage gap (the "donut hole") where beneficiaries paid more out of pocket. Thanks to the Inflation Reduction Act, the donut hole has been effectively closed, with a $2,000 annual out-of-pocket cap now in place for 2025 and beyond

Understanding these costs is essential when comparing plans in WA. For a full breakdown of the coverage gap and how it affects your spending, read our article on the Medicare Part D donut hole.

Who Is Eligible for Part D in Washington?

If you are a Washington resident enrolled in Medicare Part A, Part B, or both, you are eligible for Part D. This includes people who qualify through:

• Age (65 and older)
• Disability (under 65 with qualifying conditions)
• End-stage renal disease (ESRD)

Enrollment in Part D is voluntary, but if you don't sign up when you're first eligible and don't have other creditable drug coverage, you may face a late enrollment penalty. Check the full details in our guides on Part D eligibility and general Medicare eligibility. If you're just getting started with Medicare, our overview of what Medicare is can help you understand the basics first.

How to Enroll in Part D in Washington

There are specific windows during which Washington residents can enroll in or change a Part D plan:

• Initial Enrollment Period (IEP) — A 7-month window surrounding the month you turn 65 (3 months before, your birthday month, and 3 months after). This is your first opportunity to enroll without penalty.
• Annual Enrollment Period (AEP) — Runs from October 15 through December 7 every year. During AEP, you can join, switch, or drop a Part D plan with coverage starting January 1.
• Special Enrollment Periods (SEPs) — Triggered by qualifying life events such as moving to a new area in WA, losing other drug coverage, or qualifying for Extra Help (Low Income Subsidy).

For a complete rundown of when and how to sign up, visit our guide on Part D enrollment periods. If you're new to Medicare entirely, start with our walkthrough on how to enroll in Medicare.

Standalone Part D vs. Medicare Advantage with Drug Coverage

When choosing Part D coverage in Washington, you have two paths:

• Standalone PDP — Pairs with Original Medicare (Parts A and B). You keep the freedom to see any doctor in Washington who accepts Medicare, and you add a separate Part D plan for prescriptions.
• Medicare Advantage with drug coverage (MA-PD) — Bundles hospital, medical, and prescription drug coverage into a single plan from a private insurer. These plans often include extra benefits like dental and vision but may restrict you to a provider network within WA. Learn more about the most common Medicare Advantage questions.

The right choice depends on your healthcare needs, preferred Washington providers, and how much flexibility you want. Neither option is universally better — it comes down to your individual situation.

Late Enrollment Penalties

If you go 63 or more consecutive days without Part D or other creditable prescription drug coverage, you may owe a late enrollment penalty when you do sign up. The penalty is calculated as 1% of the national base beneficiary premium (which is $36.78 in 2026) multiplied by the number of full months you were without coverage.

This penalty is added to your monthly Part D premium for as long as you have Part D coverage — it doesn't go away. For example, if you went 24 months without creditable coverage, your penalty would be about $8.83 per month, every month, on top of your plan's regular premium. To learn more about this and other Medicare penalties, including how to avoid common Medicare mistakes, review our dedicated guides.

How to Choose the Right Part D Plan in Washington

Picking the best Part D plan in WA isn't just about finding the lowest premium. Here's what to evaluate:

• Formulary — Make sure your current medications are on the plan's drug list, and check which tier they fall under
• Pharmacy network — Confirm that your preferred Washington pharmacy (or mail-order option) is in-network for the best pricing
• Star ratings — Medicare assigns each plan a star rating from 1 to 5. Plans with 4+ stars tend to offer better service and coverage
• Total cost — Look beyond the premium. Factor in the deductible, copays for your specific drugs, and any coverage gap costs to get a true picture of annual spending

The best way to find the right fit is to compare different plans using your actual prescriptions and pharmacy. Plans change every year, so it's worth reviewing your options during every Annual Enrollment Period. For more frequently asked questions, check out our Part D FAQ.