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

Ruth Williamson, MD

Individual provider Radiation Oncology Physician · NPI 1952486912

Ruth Williamson, MD is a Radiation Oncology in Pasadena, California. Graduated from University of Southern California Keck School of Medicine in 1989, 37 years ago. Practices with Cedars-Sinai Medical Care Foundation, a 1,696-clinician group, works from 2 locations and accepts Medicare assignment. Licensed in California.

Years since qualifying
37
Trained at
University of Southern California Keck 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.

See every abbreviation used in this directory →

Practice location Address checks out

625 S Fair Oaks Ave Ste 100
Pasadena, CA 91105-2640
Phone: (626) 397-5149
Fax: (310) 397-2147
Show map & directions

Pin is approximate — placed at the ZIP-code centre, not the exact door.

Additional practice locations (1)

  • 100 W California Blvd, Pasadena, CA 91105-3010 — (626) 397-5149

Specialties & licences

Radiation Oncology Physician (primary) Taxonomy 2085R0001X · Licence G707B5C (CA)

Record details

NPI number1952486912
Entity typeIndividual (Type 1)
GenderFemale
Credentials MD
Sole proprietorNo
NPI enumeratedOctober 26, 2006
Last updated in NPPESOctober 13, 2022
Certification dateOctober 13, 2022
Mailing address4140 W 190th St, Torrance, CA 90504-5513

Medicare enrollment

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

Medicare specialtyRADIATION ONCOLOGY
Medical schoolUNIVERSITY OF SOUTHERN CALIFORNIA KECK SCHOOL OF MEDICINE
Graduated 1989 (37 years in practice)
Group practice Cedars-Sinai Medical Care Foundation — 1696 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount