TRYNYTYhealth:enablement
MA Enrollment Explorer / States / Washington

Medicare Advantage in Washington: enrollment, penetration and market share

790,581 people in Washington were enrolled in Medicare Advantage in October 2026. 49.6% of the state's 1,593,638 eligible Medicare beneficiaries are in Medicare Advantage, −0.1 pts since October 2025. UnitedHealth Group, Inc. is the largest parent organization with 46% of reported enrollment; 21 parent organizations have 11 or more members, and the market's HHI is 2,765 (highly concentrated). Through the 2026 Annual Election Period (December to February), reported MA enrollment in Washington changed by +7,096 (+0.9%).

49.6%MA penetration, October 2026
791KMA enrollees
21parent organizations (11+ members)
2,765HHI, highly concentrated
Open Washington on the market mapMSSP ACOs in Washington

Parent organizations in Washington

Parent organizationMembersChangeShareShare change
UnitedHealth Group, Inc.358,576+5,38145.5%−0.3 pts
Humana Inc.144,189+27,55518.3%+3.2 pts
Kaiser Foundation Health Plan, Inc.129,072−1,32416.4%−0.5 pts
CVS Health Corporation60,924−10,2777.7%−1.5 pts
Centene Corporation33,381−8154.2%−0.2 pts
Cambia Health Solutions, Inc.18,634−3,4992.4%−0.5 pts
Molina Healthcare, Inc.13,039−8451.7%−0.1 pts
Community Health Plan of Washington8,825−5,2921.1%−0.7 pts
Devoted Health, Inc.5,068+3,1630.6%+0.4 pts
Providence St Joseph Health4,396−5310.6%−0.1 pts
Elevance Health, Inc.4,049+1800.5%+0.01 pts
SCAN Group3,479+3,4640.4%+0.4 pts
Providence Health & Services1,377+1240.2%+0.01 pts
Health Care Service Corporation914−1900.1%−0.03 pts
Blue Cross Blue Shield of Michigan Mutual Ins. Co.469+8under 0.1%−0.00 pts
California Physicians' Service355+6under 0.1%−0.00 pts
MultiCare Health Systems322+105under 0.1%+0.01 pts
Highmark Health270−15under 0.1%−0.00 pts
Marquis Companies I, Inc.171newunder 0.1%+0.02 pts
International Community Health Services129+20under 0.1%+0.00 pts

Change and share change are since October 2025. Shares are of reported enrollment in the CMS State/County/Contract file.

Counties

CountyMA enrolleesPenetrationLeading parent
King County198,65353.7%UnitedHealth Group, Inc. 44%
Pierce County92,11451.9%UnitedHealth Group, Inc. 55%
Snohomish County91,83559.6%UnitedHealth Group, Inc. 53%
Clark County73,72767.7%Kaiser Foundation Health Plan, Inc. 30%
Spokane County71,15957.7%UnitedHealth Group, Inc. 60%
Thurston County37,26852.7%UnitedHealth Group, Inc. 45%
Kitsap County27,07440.1%UnitedHealth Group, Inc. 33%
Whatcom County25,35646.5%UnitedHealth Group, Inc. 37%
Yakima County21,87346.4%UnitedHealth Group, Inc. 59%
Cowlitz County19,68966.8%Kaiser Foundation Health Plan, Inc. 38%
Skagit County16,21645.0%UnitedHealth Group, Inc. 51%
Benton County13,67132.5%UnitedHealth Group, Inc. 53%
Lewis County13,19956.4%UnitedHealth Group, Inc. 76%
Island County11,36541.5%UnitedHealth Group, Inc. 60%
Mason County9,03844.6%UnitedHealth Group, Inc. 46%
Chelan County8,13039.8%Centene Corporation 52%
Clallam County6,95323.3%UnitedHealth Group, Inc. 77%
Grant County6,76436.6%Humana Inc. 42%
Grays Harbor County5,36723.7%Centene Corporation 51%
Stevens County5,17834.2%Humana Inc. 73%
Walla Walla County4,97233.0%UnitedHealth Group, Inc. 45%
Franklin County4,80737.2%UnitedHealth Group, Inc. 56%
Douglas County3,90640.5%Centene Corporation 50%
Okanogan County3,54028.9%Centene Corporation 39%
Kittitas County2,92726.8%Humana Inc. 53%
Jefferson County2,63717.0%UnitedHealth Group, Inc. 42%
Whitman County1,99028.0%UnitedHealth Group, Inc. 51%
Asotin County1,83326.1%Centene Corporation 64%
Pacific County1,80219.2%UnitedHealth Group, Inc. 38%
Pend Oreille County1,36528.4%Centene Corporation 36%
San Juan County1,13916.7%Centene Corporation 34%
Adams County98834.8%Centene Corporation 43%
Wahkiakum County78045.5%Kaiser Foundation Health Plan, Inc. 48%
Skamania County76123.5%Devoted Health, Inc. 26%
Klickitat County74010.2%Humana Inc. 45%
Ferry County69426.8%Centene Corporation 56%
Lincoln County66717.6%Humana Inc. 48%
Columbia County31022.7%Humana Inc. 40%
Garfield County9413.5%Centene Corporation 57%