Medicare Advantage in Custer County, Montana
408 people in Custer County, Montana were enrolled in Medicare Advantage in October 2026, 14.2% of 2,879 eligible beneficiaries (−0.5 pts since October 2025). Health Care Service Corporation is the largest parent organization with 95% of reported enrollment; 2 parent organizations have 11 or more members and the HHI is 9,109 (highly concentrated). HRSA classifies the county as fully rural. For 2027, 347 members here are in plans that terminate or leave the county, and Health Care Service Corporation leaves.
Parent organizations in Custer County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| Health Care Service Corporation | 367 | +47 | 95.3% |
| UnitedHealth Group, Inc. | 18 | 0 | 4.7% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 1,277 beneficiaries in Custer County were assigned to 10 Medicare Shared Savings Program ACOs, 78.1% of assignable Original Medicare beneficiaries. Together, roughly 81% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.