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Medicare Advantage Enrollment Tracker · Washington

Medicare Advantage Enrollment in Washington

Washington had 789,538 Medicare Advantage members in September 2026, by the CMS county file, which includes employer group plans. That is up 2.2% from Sep 2025, close to the national 2.0%. Washington ranks 14th by members and holds 2.2% of the national total.

UnitedHealthcare leads with 45.6% of members who have a carrier label (contract file, September 2026). Among individual plans, which leave out employer group coverage, enrollment is up 2.6% in the 12 months to September 2026.

By Senior Deal Club Standards Desk · Data as of September 2026 · Editorial policy

Data as ofCMS public files, monthly snapshot

  • These totals include employer and union group plans.
    Why this matters

    The CMS contract and county files count group plans that retirees get through a former employer. They are not plans you can pick on your own. Counts here are larger than the individual-plan counts on county pages.

  • Some months are missing from the source.
    Why this matters

    CMS did not publish every month. Lines break at a missing month instead of guessing a value. A dotted line, where shown, only joins the two sides.

Washington at a glance

Medicare Advantage members

789,538

Washington members by month: from 645K in Jan 2023 to 790K in Sep 2026

County file · Sep 2026. Includes employer group plans. Rank: 14.

County file · Sep 2026
CMS state, county and plan-type file (SCP). The same plans split by state and county, with employer and union group plans included. CMS hides counts of 10 or fewer.

12-month change

+2.2%

up 2.2 percent vs Sep 2025

County file · Sep 2026. National: +2.0%.

Share of national total

2.2%

County file · Sep 2026. Of jurisdictions that report every month.

Individual plan members

668,103

Individual MA · Sep 2026. Employer group plans left out.

Individual MA · Sep 2026
Individual Medicare Advantage plans (IND), from county data. Employer and union group plans are left out, so counts are smaller than in the other two files.

Largest carrier

UnitedHealthcare

45.6% of members with a carrier label. Contract file · Sep 2026.

Washington members by month

Medicare Advantage members in Washington

Members, by month.

County file · Sep 2026
CMS state, county and plan-type file (SCP). The same plans split by state and county, with employer and union group plans included. CMS hides counts of 10 or fewer.
Medicare Advantage members in WashingtonLine chart, January 2023 to September 2026. Washington: 790K in September 2026. Shaded bands mark months with no data.600K650K700K750K800K2023202420252026Washington790K
Medicare Advantage members in WashingtonLine chart, January 2023 to September 2026. Washington: 790K in September 2026. Shaded bands mark months with no data.600K650K700K750K800K20232025Washington790K
  • Washington
  • Shaded: no data that month
View the data table
Medicare Advantage members in Washington: values by month
MonthWashington
Sep 2026790K
Aug 2026790K
Jul 2026789K
Jun 2026788K
May 2026787K
Apr 2026786K
Mar 2026785K
Feb 2026783K
Jan 2026773K
Dec 2025776K
Nov 2025775K
Oct 2025774K
Sep 2025773K
Aug 2025771K
Jul 2025769K
Jun 2025768K
May 2025765K
Apr 2025764K
Mar 2025761K
Feb 2025754K
Jan 2025729K
Dec 2024783K
Nov 2024782K
Oct 2024749K
Sep 2024747K
Aug 2024745K
Jul 2024743K
Jun 2024742K
May 2024739K
Apr 2024737K
Mar 2024734K
Feb 2024732K
Jan 2024712K
Dec 2023–
Nov 2023687K
Oct 2023684K
Sep 2023681K
Aug 2023679K
Jul 2023–
Jun 2023673K
May 2023671K
Apr 2023667K
Mar 2023665K
Feb 2023662K
Jan 2023645K

County file · Sep 2026. Employer group plans included.

Washington and the nation, Jan 2023 = 100

Each line is members divided by members in the start month, times 100.

County file · Sep 2026
CMS state, county and plan-type file (SCP). The same plans split by state and county, with employer and union group plans included. CMS hides counts of 10 or fewer.
Washington and the nation, Jan 2023 = 100Line chart, January 2023 to September 2026. Washington: 122.4 in September 2026. National (same jurisdictions each month): 117.8 in September 2026. Shaded bands mark months with no data.1001101201302023202420252026Washington122.4National117.8
Washington and the nation, Jan 2023 = 100Line chart, January 2023 to September 2026. Washington: 122.4 in September 2026. National (same jurisdictions each month): 117.8 in September 2026. Shaded bands mark months with no data.10011012013020232025Washington122.4National117.8
  • Washington
  • National (same jurisdictions each month)
  • Shaded: no data that month
View the data table
Washington and the nation, Jan 2023 = 100: values by month
MonthWashingtonNational (same jurisdictions each month)
Sep 2026122.4117.8
Aug 2026122.4117.8
Jul 2026122.3117.5
Jun 2026122.2117.4
May 2026122117.2
Apr 2026121.9116.9
Mar 2026121.7116.7
Feb 2026121.3116.3
Jan 2026119.7114.7
Dec 2025120.2115.9
Nov 2025120.2115.9
Oct 2025120115.7
Sep 2025119.8115.5
Aug 2025119.5115.3
Jul 2025119.3115
Jun 2025119114.8
May 2025118.7114.4
Apr 2025118.4114.2
Mar 2025118113.8
Feb 2025116.9113.4
Jan 2025113111.9
Dec 2024121.3112
Nov 2024121.2112
Oct 2024116.1111.7
Sep 2024115.8111.5
Aug 2024115.5111.2
Jul 2024115.1110.9
Jun 2024115110.7
May 2024114.6110.5
Apr 2024114.2110
Mar 2024113.8109.7
Feb 2024113.5109.3
Jan 2024110.4108.7
Dec 2023––
Nov 2023106.5105.9
Oct 2023106105.6
Sep 2023105.6105.2
Aug 2023105.2104.9
Jul 2023––
Jun 2023104.3104.1
May 2023104103.8
Apr 2023103.5103.4
Mar 2023103.1103
Feb 2023102.7102.2
Jan 2023100100

County file · Sep 2026. National line sums the jurisdictions that report in every month.

Individual plans

Individual plans leave out employer and union group coverage, so counts are smaller than in the county file.

Carrier share in Washington

Share of members whose contract has a carrier label, September 2026 against September 2025.

Contract file · Sep 2026
CMS contract file (SCC). All Medicare Advantage contracts, with employer and union group plans included. It still lists Connecticut and Alaska.

UnitedHealthcare leads with 45.6% of members who have a carrier label (contract file, September 2026).

Humana gained 3.2 points in 12 months; most of that change came in January 2026.

UnitedHealthcare and Humana together hold 64.0%, up 2.9 points from Sep 2025.

The market is about as concentrated as a year earlier (direction only; the level depends on how carriers are grouped).

Carrier share, Sep 2025 to Sep 2026

Percent of members with a carrier label. Largest carriers.

Carrier share, Sep 2025 to Sep 2026Slope chart comparing Sep 2025 with Sep 2026. UnitedHealthcare: 45.9% to 45.6%; Humana: 15.2% to 18.3%; Kaiser: 17.0% to 16.4%; Aetna/CVS: 9.3% to 7.8%; Centene/Wellcare: 4.4% to 4.3%; Regence/BCBS: 2.8% to 2.4%.Sep 2025Sep 2026UnitedHealthcare 45.9%45.6% UnitedHealthcareHumana 15.2%18.3% HumanaKaiser 17.0%16.4% KaiserAetna/CVS 9.3%7.8% Aetna/CVSCentene/Wellcare 4.4%4.3% Centene/WellcareRegence/BCBS 2.8%2.4% Regence/BCBS
Carrier share, Sep 2025 to Sep 2026Slope chart comparing Sep 2025 with Sep 2026. UnitedHealthcare: 45.9% to 45.6%; Humana: 15.2% to 18.3%; Kaiser: 17.0% to 16.4%; Aetna/CVS: 9.3% to 7.8%; Centene/Wellcare: 4.4% to 4.3%; Regence/BCBS: 2.8% to 2.4%.Sep 2025Sep 2026UHC 45.9%45.6%Humana 15.2%18.3%Kaiser 17.0%16.4%Aetna 9.3%7.8%Centene 4.4%4.3%Blue Cross 2.8%2.4%
View the data table
Carrier share, Sep 2025 to Sep 2026: Sep 2025 and Sep 2026
NameSep 2025Sep 2026Change
UnitedHealthcare45.9%45.6%−0.3 pts
Humana15.2%18.3%+3.2 pts
Kaiser17.0%16.4%−0.5 pts
Aetna/CVS9.3%7.8%−1.5 pts
Centene/Wellcare4.4%4.3%−0.2 pts
Regence/BCBS2.8%2.4%−0.5 pts

Contract file · Sep 2026. Employer group plans included.

Carrier share of Medicare Advantage members with a carrier label, Washington, September 2026
CarrierShare, Sep 2026Share, Sep 2025ChangeMembers
UnitedHealthcare45.6%45.9%−0.3 pts357,970
Humana18.3%15.2%+3.2 pts143,815
Kaiser16.4%17.0%−0.5 pts129,001
Aetna/CVS7.8%9.3%−1.5 pts60,880
Centene/Wellcare4.3%4.4%−0.2 pts33,413
Regence/BCBS2.4%2.8%−0.5 pts18,663
Molina1.7%1.8%−0.1 pts13,090
Community Health Plan of Washington1.1%1.8%−0.7 pts8,826
All other carriers0.7%––5,285
Devoted Health0.6%0.2%+0.4 pts5,008
Providence St Joseph Health0.6%0.6%−0.1 pts4,389
Elevance/Anthem0.5%0.5%0.0 pts4,046

Insurer not assigned in CMS data: 0.4% of all members in Sep 2026, 0.5% in Sep 2025. Shares leave these members out. Contract IDs are renumbered each January, so this page follows carriers, not contracts. A contract that serves several states carries one carrier label, so a carrier can appear in a state where it is not a local plan. See the carrier view for the whole nation.

Biggest counties in Washington

Individual plan members and the 12-month change for each county, from county data.

Individual MA · Sep 2026
Individual Medicare Advantage plans (IND), from county data. Employer and union group plans are left out, so counts are smaller than in the other two files.
Biggest counties in Washington by individual Medicare Advantage members, September 2026
CountyMembers12-month changeLeading carrierLeader's share
King167,129+1.6%UnitedHealthcare47.5%
Snohomish80,398+2.0%UnitedHealthcare56.6%
Pierce79,896+2.8%UnitedHealthcare58.7%
Clark64,662+3.3%Humana29.8%
Spokane63,473+2.4%UnitedHealthcare63.0%
Thurston27,139+1.9%UnitedHealthcare49.9%
Whatcom21,541+1.8%UnitedHealthcare40.1%
Kitsap20,893+4.1%UnitedHealthcare34.7%
Yakima19,498+1.1%UnitedHealthcare57.5%
Cowlitz17,870+2.9%UnitedHealthcare39.6%

Browse all counties.

Common questions

How many people have Medicare Advantage in Washington?

Washington had 789,538 members in September 2026, by the CMS county file (employer group plans included). Individual plans, which leave out employer group coverage, had 668,103 members in September 2026.

Is Medicare Advantage growing in Washington?

Enrollment is up 2.2% from Sep 2025 to Sep 2026, close to the national 2.0%. Among individual plans, which leave out employer group coverage, enrollment is up 2.6% in the 12 months to September 2026.

Which carrier has the most Medicare Advantage members in Washington?

UnitedHealthcare leads with 45.6% of members who have a carrier label (contract file, September 2026). UnitedHealthcare and Humana together hold 64.0%, up 2.9 points from Sep 2025. Shares leave out members whose contract has no carrier label: 0.4% of members.

Cite and download

Cite this page

Senior Deal Club Standards Desk. Medicare Advantage Enrollment in Washington, data as of September 2026. Source: CMS public enrollment files. https://www.seniordealclub.com/medicare-advantage/enrollment/states/washington

Download Washington CSV

Data: CMS public enrollment files, in a monthly snapshot processed by TapQuality. Senior Deal Club is not affiliated with Medicare or any government agency.

These pages are educational. They are not plan advice. How the numbers are built · Editorial policy