Mark Williams, MD
NPI 1770661530 · Emergency Medicine Physician · Santa Rosa, CA
Enrolled with Medicare as Practitioner - Emergency Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Williams, MD is a Emergency Medicine Physician provider in Santa Rosa, CA (NPI 1770661530).
Provider details
- NPI number
- 1770661530
- Entity type
- Individual
- Primary specialty
- Emergency Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- A72120 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure38% of score
19 yrs in NPPES registry
- Profile completeness38% of score
100% of core fields populated
- Practice footprint23% of score
1 documented practice location
Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 7 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Ondansetronbrand: Ondansetron Odt | 27 | 27 |
| Prednisone | 25 | 25 |
| Hydrocodone/Acetaminophenbrand: Hydrocodone-Acetaminophen | 17 | 17 |
| Cefpodoxime Proxetil | 16 | 16 |
| Doxycycline Monohydrate | 14 | 14 |
| Cephalexin | 11 | 11 |
| Ciprofloxacin Hcl | 11 | 11 |
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-11-01
- Last updated
- 2024-04-05
- Certified
- 2024-04-05
Frequently asked questions
- What is Mark Williams's NPI number?
- Mark Williams's National Provider Identifier (NPI) is 1770661530, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Williams's specialty?
- Mark Williams is listed in the NPPES registry with a primary specialty of Emergency Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Williams located?
- Mark Williams's practice location on file with NPPES is 401 Bicentennial Way, Santa Rosa, CA 95403-2149.
- What is Mark Williams's phone number?
- The practice phone number listed in the NPPES registry for Mark Williams is (707) 393-4800.
- Does Mark Williams accept Medicare?
- Mark Williams is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Williams's NPI active?
- Yes — Mark Williams's NPI (1770661530) is active in the NPPES registry as of the last update on 2024-04-05.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.