A Plain-English Guide to Medicare Advantage in SeaTac, Washington (2027)

21 Medicare Advantage plans in King County are changing for 2027, 27 plans are leaving and 18 plans are new. Use this guide to see how the plans work in SeaTac, Washington and what to compare, in plain terms.

59 Medicare Advantage plans are available for 2027. Because SeaTac is served by King County (part of SeaTac area), those are the options on the table locally. About 54% of the county's Medicare members are in a Medicare Advantage plan rather than Original Medicare, among the roughly 320,899 residents who are 65 or older.

It surprises people, but Medicare plan availability is drawn up county by county rather than by city or state — which is why a guide like this attributes everything to the surrounding county.

Read on for the organizations offering coverage in the area, a plain-language tour of how Medicare works, 2027 costs, enrollment timing, and free places to get unbiased help. We don't rank or recommend specific plans.

How your Medicare choices fit together

Almost everyone starts with Original Medicare — Part A (hospital) and Part B (medical), run by the federal government. From there, you generally choose one of two directions, and understanding the fork is the whole game.

The Medicare Advantage path (Part C). You get your Part A and Part B benefits through a private plan approved by Medicare, usually with drug coverage included. Plans work within networks and service areas set at the county level, which is why availability in SeaTac, Washington depends on your county, not just your state.

The Original Medicare path. You stay with the government program and can add a stand-alone Part D drug plan, and often a Medigap policy to help with the out-of-pocket costs Original Medicare leaves behind — trading bundled extras for broad provider freedom.

Neither path is universally better; the right fit depends on your doctors, your prescriptions, your budget, and how you like to handle care. This guide explains how each works in SeaTac, Washington so you can decide for yourself. We don't rank or recommend specific plans.

What Medicare costs in 2027

It helps to separate the costs everyone shares from the costs that vary by plan. The program-level numbers here are set nationally — the same whether you're in a big city or a rural county.

Part B premium. Most people pay the standard Part B premium of $202.90 a month in 2026 (2026 amount; 2027 figure will be posted when CMS releases it). Part A is premium-free for most people who worked and paid Medicare taxes long enough.

Part D drug costs. In 2027, a Part D plan's yearly deductible can be no more than $700, and a $2,400 cap limits what you pay out of pocket for covered prescriptions across the year — a real change for anyone with high drug costs.

Higher earners pay more for Parts B and D through an income-related adjustment called IRMAA, which for 2026 starts above $109,000 in annual income for an individual and is based on your 2024 tax return. Most people fall below that line and pay the standard amounts. The 2027 brackets will be posted when CMS releases them.

Plan-specific costs. What an individual plan charges — its premium, deductible, copays, and what it covers — varies by plan and changes yearly. We don't publish those figures or rank plans; Medicare's Plan Finder shows the current details for your situation, and a licensed agent can walk you through them.

When you can enroll or make changes

Medicare's enrollment windows are federal — the same nationwide — so the timing below applies wherever you live.

Your first window (IEP). When you're new to Medicare, your Initial Enrollment Period is the 7-month window around your 65th birthday month. Signing up on time helps you avoid late penalties that can follow you for years.

Annual Enrollment Period (AEP). Each fall, from October 15 – December 7, anyone with Medicare can join, switch, or drop a Medicare Advantage or Part D plan. Changes take effect January 1.

Medicare Advantage Open Enrollment. From January 1 – March 31, if you're already in an Advantage plan you get one chance to switch plans or return to Original Medicare.

Special Enrollment Periods can also open after certain life events, like moving or losing other coverage. The interactive calendar further down lays the year out visually.

Getting unbiased help in SeaTac

You never have to make these decisions alone, and you don't have to pay for good help. A few free, trustworthy starting points:

Medicare.gov and 1-800-MEDICARE (TTY 1-877-486-2048) are the official sources for plan details and the Plan Finder. Licensed agents can also compare options with you and handle enrollment.

And to be clear about who we are: MyMedicarePlans.org is a privately owned, independent educational resource. We are not Medicare, not a government agency, and not affiliated with one. We publish plain-language information to help you get oriented — then point you to the official sources and licensed professionals for decisions about specific plans.

More Washington Medicare Advantage guides