Theresa Thanh Ngoc Nguyen, M.D.
NPI 1003893801ActiveIndividual· Internal Medicine· Santa Ana, CA
Internal Medicine (M.D.) in Santa Ana, California, trained at University of California, San Diego School of Medicine (class of 1995). Their prescriptions cost Medicare Part D more than their services did: $3,178,774 for 16,835 claims, against $201,169 paid for services in 2024. Mayne Pharma Commercial LLC was the largest of 17 companies reporting payments in 2025, $1,666 in all, mostly food and beverage.
Overview
| NPI | 1003893801 |
|---|---|
| Status | Active |
| Entity type | Individual |
| Credential | M.D. |
| Sole proprietor | No |
| NPI issued | Dec 22, 2005 |
| Last updated in NPPES | Jul 20, 2026 |
| Certified by provider | Jul 20, 2026 |
Specialties and licenses
| Taxonomy | Code | License | State |
|---|---|---|---|
| Internal Medicine Primary | 207R00000X | A61129 | CA |
Exclusion screening
| List | Result | Details |
|---|---|---|
| HHS-OIG LEIE · Oct 9, 2026 | No match | Checked by NPI and by name + state |
| North Carolina Medicaid · Nov 4, 2026 | No match | — |
| New York OMIG · Nov 4, 2026 | No match | — |
| Ohio Medicaid · Nov 4, 2026 | No match | — |
| Pennsylvania Medicheck · Nov 4, 2026 | No match | — |
| Washington HCA · Nov 4, 2026 | No match | — |
Official OIG search · How matching works ·Bulk check a roster
Medicare
| Enrollment (PECOS) | Enrolled Practitioner - Internal Medicine (CA) |
|---|---|
| Accepts assignment | Yes (participating) |
Medicare services in 2024
| Medicare patients | 463 |
|---|---|
| Services billed | 3,664 across 20 procedure codes |
| Paid by Medicare | $201,169 |
Part D prescriptions in 2024
| Prescriptions (claims) | 16,835 · 37,031 30-day fills |
|---|---|
| Patients | 866 |
| Total drug cost | $3,178,774 |
| Generic share | 79% of claims |
Education and affiliations
| Medical school | University of California, San Diego School of Medicine |
|---|---|
| Graduation year | 1995 |
| Medicare specialty | Internal Medicine |
Medical groups
- Family Choice ACO IncWestminster, CA · 55 clinicians
- Theresa Thanh Ngoc Nguyen MD IncSanta Ana, CA · 2 clinicians
Industry payments (Open Payments)
- 2025$1,666 · 74 payments from 17 companies
- 2024$1,646 · 53 payments from 20 companies
Top paying companies in 2025
| Company | Amount | Payments |
|---|---|---|
| Mayne Pharma Commercial LLC | $246.07 | 2 |
| Astrazeneca Pharmaceuticals LP | $244.08 | 25 |
| Gilead Sciences, Inc. | $226.22 | 5 |
| Amgen Inc. | $186.61 | 11 |
| Ardelyx, Inc. | $181.06 | 5 |
What the 2025 payments were for
- Food and Beverage$1,666 · 74 payments
Receiving payments does not imply wrongdoing. What Open Payments covers ·original records
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