William Mathias, PA-C
NPI 1285806323 · Physician Assistant · San Marcos, CA
Enrolled with Medicare as Practitioner - Physician Assistant · source: CMS PECOS Public Provider Enrollment (2026.04.01)
William Mathias, PA-C is a Physician Assistant provider in San Marcos, CA (NPI 1285806323).
Provider details
- NPI number
- 1285806323
- Entity type
- Individual
- Primary specialty
- Physician AssistantPhysician Assistants & Advanced Practice Nursing Providers
- Credential
- PA-C
- Sex
- Male
- Sole proprietor
- No
- License
- 085.004666 (IL)
Specialties & taxonomies
Physician Assistants & Advanced Practice Nursing Providers
Physician Assistants & Advanced Practice Nursing Providers
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure33% of score
18 yrs in NPPES registry
- Profile completeness33% of score
100% of core fields populated
- Practice footprint20% of score
1 documented practice location
- Open Payments transparency13% of score
Has Open Payments disclosures (2024)
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) |
|---|---|
| Levothyroxine Sodium | 27 |
| Amlodipine Besylate | 14 |
| Metformin Hcl | 14 |
| Lisinopril | 13 |
| Rosuvastatin Calcium | 12 |
| Losartan Potassium | 12 |
| Omeprazole | 11 |
Medicare Part D only. These counts cover prescriptions paid through Medicare Part D in 2024 — they do notinclude cash-pay, commercial-insurance, Medicaid, or Part B–administered drugs, and badly undercount high cash-pay categories (e.g. GLP-1 weight-loss, testosterone, and ED medications). Any drug with 10 or fewer claims is omitted by CMS, and beneficiary counts under 11 are suppressed — so a missing drug means , never zero. This is a factual claims summary, not an endorsement, not medical advice, and not a consumer report. Source: CMS Medicare Part D Prescribers — by Provider and Drug.
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$224 across 9 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2008-03-28
- Last updated
- 2023-03-28
- Certified
- 2023-03-28
Frequently asked questions
- What is William Mathias's NPI number?
- William Mathias's National Provider Identifier (NPI) is 1285806323, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is William Mathias's specialty?
- William Mathias is listed in the NPPES registry with a primary specialty of Physician Assistant (Physician Assistants & Advanced Practice Nursing Providers).
- Where is William Mathias located?
- William Mathias's practice location on file with NPPES is 150 Valpreda Rd, San Marcos, CA 92069-2973.
- What is William Mathias's phone number?
- The practice phone number listed in the NPPES registry for William Mathias is (760) 736-6767.
- Does William Mathias accept Medicare?
- William Mathias is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is William Mathias's NPI active?
- Yes — William Mathias's NPI (1285806323) is active in the NPPES registry as of the last update on 2023-03-28.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.