Ferrin K. Ruiz, MD

Practice locations

Addresses where Ferrin K. Ruiz is enrolled with Medicare (CMS data updated 2026-10-02).

• 403 W F StOntario, CA 91762 (909) 988‑3288
• 833 W Whittier BlvdMontebello, CA 90640 (323) 712‑4811

Group practices

Medicare enrollment lists Ferrin K. Ruiz as a member of these groups (CMS data updated 2026-10-02).

• R. Ruiz MD a Professional Corporation3 clinicians in the group
• Ruben Ruiz M D A Medical Corporation2 clinicians in the group

Specialties

• Internal Medicineprimary
• Pediatric Medicinealso

Find other Internal Medicine doctors in California →

Other internal medicine doctors in Ontario

Clinicians with the same Medicare primary specialty in Ontario, CA — not a recommendation.

• David C. Wang, MD
• Haik Yanashyan, MD
• Glory Y. Tseng, DO
• Anu Mittal, DO
• Charles I. Lu, MD
• Michael Arden G. Perdon, MD
• Shreyas Srinivas, MD
• Austin Smith, MD

All internal medicine doctors in Ontario →

Clinician information

Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.

Sources

1. National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
2. NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
3. Medicare Care Compare — official Medicare tool to look up clinicians