Dr. William W. Chen, MD
Internal Medicine (Internal Medicine Physician)
2089 Vale Rd, #34
San Pablo, CA 94806
Who else practices at this address →
Contra Costa County includes mental health (19% of residents) shortage areas. About shortage areas
- Medicare participating
At a glance
- Medical school
- Js Weill Medical College, Cornell University (1998)
- Years since graduation
- 28
- In the NPI registry since
- 2006
- Medicare patients seen, 2024
- 496
Licensed in California since 1999, according to the Medical Board of California. We show license dates only for the states that publish them in bulk; see which states do. For other states, check the state medical board.
The NPI date is when this clinician registered for a National Provider Identifier, the billing number used on health claims. It is not a license, graduation or board-certification date. NPIs were first issued in May 2005 and became required on claims in 2007–2008, so an early date usually means the clinician was already in practice before then. What an NPI is
Education and training
- 1998Medical school: Js Weill Medical College, Cornell University
- 2006Registered with an NPI (national billing number; not a license date) — NPIs began in 2005, so practice likely started earlier
Undergraduate school, residency, fellowship, licensing exams and board certification aren’t in public federal data. Board certification can be confirmed with the certifying board (ABMS member boards for MDs, AOA boards for DOs).
Specialties and state licenses
-
Internal Medicine Physician primary
CA license A070200 (first issued 1999; current) -
Allergy & Immunology Physician
CA license A070200 (first issued 1999; current)
As reported to the NPI registry. To confirm a license is current, check the state medical board.
Where they work
Hospitals
- Stanford Health Care Stanford, CA
- John Muir Medical Center - Walnut Creek Campus Walnut Creek, CA
- Alta Bates Summit Medical Center Oakland, CA
- Alta Bates Summit Medical Center - Alta Bates Camp Berkeley, CA
- Contra Costa Regional Medical Center Martinez, CA
Hospitals this clinician lists with Medicare, and groups they bill Medicare through (Care Compare). Affiliation doesn’t mean they see patients at every location.
Medicare patients and services
- Medicare patients, 2024
- 496
- Services billed
- 3,407
- Patients’ average age
- 75
| Service | Times | Patients |
|---|---|---|
| Established patient office or other outpatient visit, 20-29 minutes | 1,654 | 419 |
| Annual wellness visit, includes a personalized prevention plan of service (pps), subsequent visit | 295 | 295 |
| Administration of influenza virus vaccine | 232 | 226 |
| Influenza vaccine split virus, preservative free | 203 | 203 |
| Assessment of emotional or behavioral problems | 196 | 193 |
| Established patient office or other outpatient visit, 30-39 minutes | 130 | 112 |
| Physician or allowed practitioner re-certification for medicare-covered home health services under a home health plan of care (patient not present), including contacts with home health agency and review of reports of patient status required by physicians a | 72 | 40 |
| Adm sarscv2 bvl 30mcg/.3ml a | 69 | 68 |
| Annual alcohol misuse screening, 5 to 15 minutes | 50 | 50 |
| Injection of drug or substance under skin or into muscle | 44 | 11 |
Medicare fee-for-service only. CMS leaves out services billed for fewer than 11 patients. These figures describe a practice’s Medicare work; they aren’t a measure of quality.
Medicare prescriptions
Prescriptions filled under Medicare Part D, including refills. CMS leaves out drugs prescribed fewer than 11 times.
Payments from drug and device companies
In 2025, 6 companies reported 49 payments worth $949 in total to this clinician.
| Novo Nordisk Inc | $228 |
|---|---|
| AstraZeneca Pharmaceuticals LP | $217 |
| Madrigal Pharmaceuticals | $177 |
| Sumitomo Pharma America, Inc. | $172 |
| AbbVie Inc. | $139 |
| Ardelyx, Inc. | $15.89 |
| Food and Beverage | $909 |
|---|---|
| Education | $39.56 |
What the payments were for
| Company | What it was for | Amount |
|---|---|---|
| Madrigal Pharmaceuticals Jun 11, 2025 | Education REZDIFFRA · LIVER DISEASE · in-kind | $39.56 |
Each payment as the company reported it, with the products it named. Meals are counted in the totals above but not listed one by one.
From CMS Open Payments. A payment is not evidence of wrongdoing; many are for consulting, teaching or meals. Clinicians can review and dispute their records with CMS.