Medicare Advantage in Mason County, Washington
9,038 people in Mason County, Washington were enrolled in Medicare Advantage in October 2026, 44.6% of 20,274 eligible beneficiaries (+0.6 pts since October 2025). UnitedHealth Group, Inc. is the largest parent organization with 46% of reported enrollment; 8 parent organizations have 11 or more members and the HHI is 3,321 (highly concentrated). HRSA classifies the county as fully rural. For 2027, 3,759 members here are in plans that terminate or leave the county. MA plans offered go from 19 to 14.
Parent organizations in Mason County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| UnitedHealth Group, Inc. | 4,151 | +369 | 46.2% |
| Kaiser Foundation Health Plan, Inc. | 2,868 | −136 | 31.9% |
| Humana Inc. | 1,022 | +196 | 11.4% |
| Centene Corporation | 441 | −116 | 4.9% |
| CVS Health Corporation | 247 | +9 | 2.8% |
| Molina Healthcare, Inc. | 129 | −21 | 1.4% |
| Elevance Health, Inc. | 86 | +13 | 1.0% |
| Cambia Health Solutions, Inc. | 36 | −7 | 0.4% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 5,844 beneficiaries in Mason County were assigned to 60 Medicare Shared Savings Program ACOs, 73.2% of assignable Original Medicare beneficiaries. Together, roughly 85% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.