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

Tommy Tiong Hien Oei, MD

Individual provider Gastroenterology Physician · NPI 1033286844

Tommy Tiong Hien Oei, MD practises Internal Medicine in Fontana, California. Graduated from New York University School of Medicine in 1997, 29 years ago. Practices with Southern California Permanente Medical Group, an 11,242-clinician group and accepts Medicare assignment. Licensed in California.

Years since qualifying
29
Trained at
New York 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

9961 Sierra Ave
Fontana, CA 92335-6720
Phone: (909) 427-3910
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Gastroenterology Physician (primary) Taxonomy 207RG0100X · Licence A66717 (CA)

Record details

NPI number1033286844
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedNovember 29, 2006
Last updated in NPPESDecember 1, 2021

Medicare enrollment

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

Medicare specialtyINTERNAL MEDICINE
Also practisesGASTROENTEROLOGY
Medical schoolNEW YORK UNIVERSITY SCHOOL OF MEDICINE
Graduated 1997 (29 years in practice)
Group practice Southern California Permanente Medical Group — 11242 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations2 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.

Upper gastrointestinal (GI) endoscopy for acid reflux 13 times · 45th percentile
Colonoscopy 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.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at Southern California Permanente Medical Group

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 11242 clinicians in the practice; 12 are shown here.

Other providers in Fontana