Theresa Thanh Ngoc Nguyen, M.D.
Internal Medicine Physician · Santa Ana, CA
Theresa Thanh Ngoc Nguyen, M.D. is an internal medicine physician with a practice address in Santa Ana, California, and NPI 1003893801, issued on Dec 22, 2005. Check the license (California A61129, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Theresa Thanh Ngoc Nguyen
- Credential
- M.D.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- A61129 CA
Self-reported in NPPES; status is on the state search - Practice location
- 5030 Westminster Ave, Santa Ana, CA 92703
- Phone
- (714) 775-8090
- Enumerated
- Dec 22, 2005
- Record last updated
- Jul 20, 2026
- Fax
- (657) 251-0494
- Medicare enrollment
- Enrolled (PECOS I20120501000264); accepts Medicare assignment
- Medical or professional school
- University Of California, San Diego School Of Medicine, 1995
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 5030 Westminster Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Tam NguyenWomen's Health Nurse Practitioner1407562853
- Thai Nguyen, M.D.Internal Medicine Physician1467547042
Verify Theresa Thanh Ngoc Nguyen in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A61129Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
5.3 times the Medicare Part D claims of the average internal medicine physician in 2024
16,835 Medicare Part D claims for 866 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 19% of claims. 55 claims were for opioids.
Most prescribed
- Atorvastatin Calcium1,040 claims
- Amlodipine Besylate858 claims
- Metformin Hcl615 claims
- Alendronate Sodium550 claims
- Losartan Potassium516 claims
- Jardiance433 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Industry payments in 2024: $1,645.53
51 payments; by number, the most common kind was food and beverage; the largest payer was AstraZeneca Pharmaceuticals LP. The 50,334 providers of this specialty with any payment received $1,303.06 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through one group practice
- Family Choice Aco IncWestminster, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Theresa Thanh Ngoc Nguyen among 17,696 internal medicine physician records in California
Theresa Thanh Ngoc Nguyen, M.D. is one of 17,696 internal medicine physician records with a practice address in California. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 95% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated1995 · median 2004 among the 11,065 with a school on file
- Record last updated2026 · 61% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Internal Medicine Physician providers in California
There are 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Santa Ana → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Kelvin Mai, DOSanta Ana, CA 927031326072612
- Thai Nguyen, M.D.Santa Ana, CA 927031467547042
- Archana Shah, MDSanta Ana, CA 927031508867136
- Robert Castro, DOSanta Ana, CA 927041285777813
- Iyad Houshan, M.D.Santa Ana, CA 927041497773287
- Wesam Houshan, MDSanta Ana, CA 927041356467112
- Ajay Meka, M.D.Santa Ana, CA 927041063527976
- Madhavi Mulye, M.D.Santa Ana, CA 927041205056470
Common questions
What is Theresa Thanh Ngoc Nguyen, M.D.'s NPI number?
Theresa Thanh Ngoc Nguyen, M.D.'s National Provider Identifier (NPI) is 1003893801, issued on Dec 22, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Theresa Thanh Ngoc Nguyen, M.D. located?
The NPPES record lists a practice address at 5030 Westminster Ave, Santa Ana, CA, 92703. Phone: (714) 775-8090. Providers update this record themselves, so call before visiting.
How can I verify Theresa Thanh Ngoc Nguyen, M.D.'s license?
NPPES lists California license number A61129, as entered by the provider. Search the Medical Board of California at https://www.mbc.ca.gov/License-Verification/default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Theresa Thanh Ngoc Nguyen, M.D. prescribe under Medicare Part D?
In 2024, Theresa Thanh Ngoc Nguyen, M.D. had 16,835 Medicare Part D claims for 866 beneficiaries; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.