Theresa Thanh Nguyen, M.D.
NPI 1003893801 · Internal Medicine Physician · Westminster, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Theresa Thanh Nguyen, M.D. is a Internal Medicine Physician provider in Westminster, CA (NPI 1003893801).
Provider details
- NPI number
- 1003893801
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Female
- Sole proprietor
- No
- License
- A61129 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
20 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
3,407 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our .
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 1,498 | $99 |
| Insertion of Needle Into Vein for Collection of Blood Sample36415 | 715 | $9 |
| Chronic Care Management Services, First 20 Minutes of Clinical Staff Time Directed By Health Care Professional, Per Calendar Month99490 | 504 | $67 |
| Administration of Influenza Virus VaccineG0008 | 206 | $35 |
| Advance Care Planning, First 30 Minutes99497 | 187 | $86 |
| Annual Wellness Visit, Includes a Personalized Prevention Plan of Service (pps), Subsequent VisitG0439 | 185 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 203 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Atorvastatin Calcium | 1,040 | 301 |
| Amlodipine Besylate | 858 | 246 |
| Metformin Hcl | 615 | 182 |
| Alendronate Sodium | 550 | 154 |
| Losartan Potassium | 516 | 164 |
| Empagliflozinbrand: Jardiance | 433 | 106 |
| Metoprolol Succinate |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$1,646 across 51 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2005-12-22
- Last updated
- 2016-04-13
Frequently asked questions
- What is Theresa Thanh Nguyen's NPI number?
- Theresa Thanh Nguyen's National Provider Identifier (NPI) is 1003893801, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Theresa Thanh Nguyen's specialty?
- Theresa Thanh Nguyen is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Theresa Thanh Nguyen located?
- Theresa Thanh Nguyen's practice location on file with NPPES is 15576 Brookhurst St Ste B, Westminster, CA 92683-7586.
- What is Theresa Thanh Nguyen's phone number?
- The practice phone number listed in the NPPES registry for Theresa Thanh Nguyen is (714) 775-8090.
- Does Theresa Thanh Nguyen accept Medicare?
- Theresa Thanh Nguyen is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Theresa Thanh Nguyen's NPI active?
- Yes — Theresa Thanh Nguyen's NPI (1003893801) is active in the NPPES registry as of the last update on 2016-04-13.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.