MA Enrollment Explorer / Parent organizations / Health Plan of San Mateo
Health Plan of San Mateo: Medicare Advantage enrollment and market share
Health Plan of San Mateo had 8,482 Medicare Advantage members in October 2026, #114 nationally with 0.02% of all MA enrollment. It gained 42 members (+0.5%) since October 2025, and has enrollment in 1 state and 7 counties with 11 or more members. In the 2026 Annual Election Period (December to February) it gained 4 members (+0.0%). For 2027, 0 of its members are in plans that terminate and 485 in plans leaving their county, and it leaves 6 counties entirely.
8,482MA members, October 2026
+0.5%change since October 2025 (+42)
0.02%national MA share, rank 114
1contracts with enrollment
Largest states
| State | Members | Share of state MA |
|---|---|---|
| California | 8,432 | 0.2% |
Largest counties
| County | Members | Change since October 2025 | Share of county MA |
|---|---|---|---|
| San Mateo County, CA | 7,947 | +149 | 10.8% |
| San Francisco County, CA | 269 | −35 | 0.3% |
| Santa Clara County, CA | 148 | −54 | 0.1% |
| Alameda County, CA | 24 | −3 | 0.0% |
| Sacramento County, CA | 22 | −2 | 0.0% |
| Sonoma County, CA | 11 | −2 | 0.0% |
| Contra Costa County, CA | 11 | −2 | 0.0% |
Contracts
| Contract | Plan type | Oct 2024 | Oct 2025 | Oct 2026 |
|---|---|---|---|---|
| H6019 HEALTH PLAN OF SAN MATEO | HMO/HMOPOS | 8,339 | 8,440 | 8,482 |
Star ratings for these contracts are in the MA Quality Dashboard.