Your Medicare Advantage Plan Is Leaving King County: What Now

CMS counted 368,813 people with Medicare in King County in July 2026. Of those, 197,594 were in Medicare Advantage and other health plans. That one county holds about a quarter of every Washington resident enrolled in that kind of coverage.

If one of those letters landed on your kitchen table, here is the short version. Your plan keeps paying claims through December 31, 2026. You can choose your 2027 coverage now. If you choose by December 31, the new coverage begins January 1 with no break. The full statewide walk-through is on our Washington plan-discontinued guide; this page sticks to what is different about King County.

How King County compares with the state

Source: CMS Medicare Monthly Enrollment, July 2026 (data.cms.gov). Counts are people, not plans. The "other health plans" figure includes cost plans and PACE.

Three things jump out. First, King leans a few points further toward Medicare Advantage than the state as a whole, 53.6% against 49.7%. More people in those plans means more people affected whenever one leaves.

Second, 190,884 people get their drug coverage bundled inside a health plan. That is the coverage that disappears with the plan. If you are one of them and you end up in Original Medicare, you have to go get a separate Part D plan yourself.

Third, the dual-eligible number. 58,692 King County residents have both Medicare and Apple Health, about 15.9% of local beneficiaries, a bit above the statewide 15.1%. Duals have extra protections and extra choices, which I cover below.

For scale: OFM put King County at 2,424,700 people on April 1, 2026, and counted 359,480 residents age 65 or older in 2025. Medicare enrollment is a little higher than the 65+ count because it also includes the 21,859 people who qualify through a disability.

Twenty-one hospitals, spread unevenly

The Washington Department of Health and CMS hospital files list 21 hospitals in King County. Most sit in Seattle, but the suburbs are not empty. When you compare 2027 options, look up the hospital you would actually go to in an emergency or for surgery, not just your primary care clinic.

Source: WA DOH hospital financial data (data.wa.gov) and CMS Hospital General Information, retrieved October 25, 2026.

Why this matters: a Medicare Advantage network that looks fine from Capitol Hill may be thin out on the Enumclaw Plateau or up in the Snoqualmie Valley. Original Medicare works at any hospital that takes Medicare, which includes all of the above except the Seattle VA, where care runs on VA eligibility rather than Medicare. If you live far from Seattle and your usual hospital is one of the two critical access hospitals, check that hospital by name in any plan you consider.

The federal rules, applied to a King County calendar

None of this is set by King County or by Washington. CMS writes the rules, and the state insurance commissioner (OIC) says plainly that it has no authority over Medicare Advantage plans. The dates for anyone whose plan ends December 31, 2026:

• Now through December 7: Medicare Open Enrollment. Anyone can switch, and changes start January 1.
• December 8 through February 28, 2027: your special enrollment period, which exists because your plan is leaving. Requests made by December 31 start January 1. A January request starts February 1; a February request starts March 1.
• December 31: the old plan's last day. Treat it as your real deadline.
• If you pick nothing: on January 1 you are in Original Medicare, Parts A and B. You will not have drug coverage unless you join a stand-alone Part D plan. The exception is people with Extra Help, whom CMS reassigns to a drug plan automatically.

The Part D gap is not just inconvenient. Go 63 days or more in a row without drug coverage and Medicare adds a late enrollment penalty to your premium for as long as you have Medicare drug coverage, unless you get Extra Help.

Medigap without health questions

Pick Original Medicare and state law steps in. Under RCW 48.66.055 a Medicare Supplement (Medigap) insurer has to accept you for certain standardized plans, without looking at your health. People first eligible for Medicare before 2020 may choose Plans A through F (including high-deductible F), K or L; people first eligible on or after January 1, 2020 choose among A, B, D, G (including high-deductible G), K or L. November 1 is the earliest OIC suggests applying, and the protection runs out March 4, 2027, 63 days past the plan's end. Hang on to the letter and the postmarked envelope; insurers can ask for proof.

You only get that right if you choose Original Medicare. Join another Medicare Advantage plan and you don't use it, and once the 63 days run out it is gone.

If you have Apple Health too

With nearly 59,000 dual-eligible residents, this deserves its own section. If you have Medicaid (Apple Health) or Extra Help, Medicare lets you change your drug coverage once a calendar month, with the change starting the first of the next month. Washington's integrated plans for duals are called Apple Health Medicare Connect, and people with full Medicaid can join or switch integrated plans monthly as well.

If money is tight and you don't have Apple Health, look at the Medicare Savings Programs run by the Health Care Authority. HCA says there is no asset test. Qualifying also makes you eligible for Extra Help with drug costs. Apply at washingtonconnection.org or see HCA's Medicare Savings Program page.

Who to call in King County

SHIBA, the state's free and unbiased Medicare counseling program, lists two King County sponsor organizations: Solid Ground and the Chinese Information and Service Center (CISC), both in Seattle. CISC is useful if you or your parent would rather talk it through in Chinese. But when I checked OIC's local listings on October 26, 2026, both carried the same notice: no appointments for now, call Medicare at 1-800-633-4227 instead. So in practice:

• SHIBA statewide: 800-562-6900, weekdays 8:30 a.m. to 4:30 p.m. Ask to be connected to local help.
• 1-800-MEDICARE (1-800-633-4227; TTY 1-877-486-2048), around the clock except some federal holidays. They can walk you through Medicare Plan Finder and take an enrollment over the phone.
• Community Living Connections, King County: 1-844-348-5464. The Area Agency on Aging for all of King County is the City of Seattle's Aging and Disability Services, under a partnership with the county.
• PEBB retirees: call the Health Care Authority at 1-800-200-1004, not Medicare. PEBB retiree open enrollment runs October 26 through November 23, 2026.

Getting to a new doctor

If the plan change means a new clinic across the county, transit can help. King County Metro's Regional Reduced Fare Permit is open to anyone 65 or older and to Medicare card holders; Metro's reduced fare is $1 per trip, and the first card has no fee. For people whose disability keeps them off regular buses, Metro's Access paratransit vans serve areas within three-quarters of a mile of regular bus and Link routes. An application has to be co-signed by a health care professional and Metro says processing typically takes up to 21 days after a complete application, so apply early if you will need rides in January.

This page is a plain-language summary. What actually governs is federal Medicare regulation plus Washington's insurance code, and the dates in your own plan's letter outrank anything written here. Run your situation past 1-800-MEDICARE, a SHIBA counselor or a licensed agent first.

Related pages: Washington statewide guide · Auburn · Bellevue · Bothell · Burien · Covington · Des Moines · Enumclaw · Federal Way · Issaquah · Kenmore · Kent · Kirkland · Lake Forest Park · Maple Valley · Mercer Island · Newcastle · Redmond · Renton · Sammamish · SeaTac · Seattle · Shoreline · Snoqualmie · Tukwila · Woodinville

King County questions we hear

Sources

1. CMS Medicare Monthly Enrollment, July 2026
2. WA OIC: Is your Medicare Advantage plan changing or leaving?
3. WA OIC: Find a local SHIBA office
4. CMS CY2027 MA and Part D Enrollment and Disenrollment Guidance
5. RCW 48.66.055 (Medigap guaranteed issue)
6. Medicare.gov: Part D costs and late enrollment penalty
7. WA HCA: Medicare Savings Program
8. King County: Older adult services
9. King County Metro: Regional Reduced Fare Permit
10. King County Metro: Access Transportation
11. WA OFM April 1, 2026 population estimates
12. WA DOH hospital data