Medicare Advantage in Williamson County, Tennessee
19,307 people in Williamson County, Tennessee were enrolled in Medicare Advantage in October 2026, 40.1% of 48,144 eligible beneficiaries (−1.2 pts since October 2025). Health Care Service Corporation is the largest parent organization with 32% of reported enrollment; 12 parent organizations have 11 or more members and the HHI is 2,198 (highly concentrated). For 2027, 827 members here are in plans that terminate or leave the county, and Centene Corporation leaves. MA plans offered go from 45 to 40.
Parent organizations in Williamson County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| Health Care Service Corporation | 6,133 | −633 | 31.9% |
| UnitedHealth Group, Inc. | 4,536 | −134 | 23.6% |
| BlueCross BlueShield of Tennessee | 3,835 | +214 | 20.0% |
| Humana Inc. | 2,543 | +711 | 13.2% |
| CVS Health Corporation | 1,223 | +85 | 6.4% |
| Elevance Health, Inc. | 420 | −45 | 2.2% |
| Blue Cross Blue Shield of Michigan Mutual Ins. Co. | 199 | −6 | 1.0% |
| Devoted Health, Inc. | 144 | +52 | 0.7% |
| Centene Corporation | 127 | −3 | 0.7% |
| California Physicians' Service | 19 | −3 | under 0.1% |
| Missouri Healthcare Advisors, LLC | 18 | +1 | under 0.1% |
| Highmark Health | 11 | new | under 0.1% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 11,533 beneficiaries in Williamson County were assigned to 149 Medicare Shared Savings Program ACOs, 60.6% of assignable Original Medicare beneficiaries. Together, roughly 76% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.