Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of August 10, 2026.
NPIDirectory

Dr. Weiyun Z Ai, MD

Individual provider Medical Oncology Physician · NPI 1649346842

Dr. Weiyun Z Ai, MD practises Medical Oncology in San Francisco, California. Graduated from Stanford University School of Medicine in 2000, 26 years ago. Practices with University of California San Francisco, a 1,793-clinician group, accepts Medicare assignment and offers telehealth. Licensed in California.

Years since qualifying
26
Trained at
Stanford University School of Medicine
Licensed in
CA
In the registry since
2006
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

400 Parnassus Ave
San Francisco, CA 94143-2202 Not confirmed with CMS for 18 years — call before visiting
Phone: (415) 353-2737
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Medical Oncology Physician (primary) Taxonomy 207RX0202X · Licence A78202 (CA)

Record details

NPI number1649346842
Entity typeIndividual (Type 1)
GenderFemale
Credentials MD
Sole proprietorNo
NPI enumeratedNovember 28, 2006
Last updated in NPPESJune 6, 2008

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyMEDICAL ONCOLOGY
Also practisesINTERNAL MEDICINE
Medical schoolSTANFORD UNIVERSITY SCHOOL OF MEDICINE
Graduated 2000 (26 years in practice)
Group practice University Of California San Francisco — 1793 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
TelehealthOffers telehealth services
Practice locations5 on file with Medicare

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Skin biopsy 1–10 times

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients222
Services billed 1,285 a service is one billed item, such as a visit, a test or a procedure
Average patient age74

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Consulting Fee $4,569 2 payments
Food and Beverage $469 7 payments · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician. Those with a page here are linked.

  • Ucsf Medical Center Hospital · San Francisco, CA
  • Marinhealth Medical Center Hospital · Greenbrae, CA

Colleagues at University of California San Francisco

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 1793 clinicians in the practice; 12 are shown here.

Other providers in San Francisco