Quick answers
- Which hospitals does Gregory S. Larsen work at?
- Medicare's official clinician data lists Gregory S. Larsen at 4 hospitals: Adventist Health Howard Memorial, Adventist Health Mendocino Coast, Marinhealth Medical Center and Sutter Santa Rosa Regional Hospital. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does Gregory S. Larsen see patients?
- Medicare's clinician data lists 4 practice locations, including Willits, CA, San Francisco, CA and Greenbrae, CA. Call before your visit to confirm the address.
- What is Gregory S. Larsen's specialty?
- Medicare lists Emergency Medicine as the primary specialty.
- Does Gregory S. Larsen accept Medicare assignment?
- Yes. Medicare's clinician data says Gregory S. Larsen accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for Gregory S. Larsen?
- (707) 994-6486, as listed in official Medicare / NPI Registry data.
- What is Gregory S. Larsen's NPI number?
- 1104073709. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where Gregory S. Larsen works
Medicare's Facility Affiliation Data lists Gregory S. Larsen at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- Adventist Health Howard MemorialWillits, CA · Critical Access Hospital · CCN 051310
- Adventist Health Mendocino CoastFort Bragg, CA · Critical Access Hospital · CCN 051325
- Marinhealth Medical CenterGreenbrae, CA · Acute Care Hospital · CCN 050360
- Sutter Santa Rosa Regional HospitalSanta Rosa, CA · Acute Care Hospital · CCN 050291
Practice locations
Addresses where Gregory S. Larsen is enrolled with Medicare (CMS data updated 2026-10-02).
- 1 Marcela DrWillits, CA 95490 (707) 994‑6486
- 1101 Van Ness AveSan Francisco, CA 94109 (415) 600‑6000
- 250 Bon Air RdGreenbrae, CA 94904 (415) 925‑7000
- 45 Castro StSan Francisco, CA 94114 (415) 600‑0600
Group practices
Medicare enrollment lists Gregory S. Larsen as a member of these groups (CMS data updated 2026-10-02).
- Cep America - California1,292 clinicians in the group
- San Francisco Emergency Medical Associates75 clinicians in the group
- Pacific Redwood Medical Group Inc58 clinicians in the group
Specialties
- Emergency Medicineprimary
Other emergency medicine doctors in Willits
Clinicians with the same Medicare primary specialty in Willits, CA — not a recommendation.
Clinician information
| Credential | DO |
|---|---|
| Graduation year | 2007 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1104073709 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated 2026-10-02, retrieved 2026-10-29
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians