1. Home
  2. Directory
  3. California
  4. Santa Ana
  5. Internal Medicine
  6. NPI Profile

THERESA THANH NGOC NGUYEN M.D.
NPI 1003893801
Internal Medicine in Santa Ana, CA

Active since December 22, 2005PECOS EnrolledAccepts Medicare AssignmentCLIA 05D0951274 · Waiver
5030 WESTMINSTER AVE, SANTA ANA, CA 92703(714) 775-8090(657) 251-0494 Get Directions Write a Review

NPPES record last updated: July 20, 2026. Verified against the NPPES registry weekly; last sync: November 01, 2026.

About Theresa Thanh Ngoc Nguyen M.d. NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

THERESA THANH NGOC NGUYEN M.D. (NPI 1003893801) is an individual internal medicine provider in Santa Ana, California, licensed in California (A61129) and active in the NPI registry since December 2005. She is enrolled in Medicare PECOS, holds a CLIA Waiver certificate valid through September 14, 2028, and is a graduate of University Of California, San Diego School Of Medicine (1995).

NPPES Registry Identity

NPI1003893801
Entity TypeIndividualFemale
Primary Taxonomy207R00000X
Provider Legal NameTHERESA THANH NGOC NGUYENCredential: M.D.
Location Address5030 WESTMINSTER AVESanta Ana, CA 92703-1151
Mailing Address5030 Westminster AveSanta Ana, CA 92703-1151 · (714) 775-8090 · Fax (657) 251-0494
Phone(714) 775-8090
Fax(657) 251-0494
Sole ProprietorNo
Medical School CMSUniversity Of California, San Diego School Of MedicineGraduated 1995
Enumeration DateDecember 22, 2005
Last NPPES UpdateJuly 20, 2026
NPPES CertifiedJuly 20, 2026
✔ NPI 1003893801 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyInternal MedicineAllopathic & Osteopathic Physicians
Taxonomy Code207R00000X
License✔ Licensed in CA · A61129
Definition
A physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults and the elderly. Internists are trained in the diagnosis and treatment of cancer, infections and diseases affecting the heart, blood, kidneys, joints and digestive, respiratory and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health and effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs.
5030 WESTMINSTER AVE, Santa Ana, CA 92703
Open in Google Maps ↗

Other Names 1

Other Name (5)Thanh Ngoc Nguyen Md

Medicare Participation & PECOS CMS

Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.

Medicare Enrollment Status

✔

Enrolled in Medicare and accepts Medicare assignment

Theresa Thanh Ngoc Nguyen M.d. is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.

PECOS PAC ID6901068378
PECOS Enrollment IDI20120501000264
Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Medicare Billing Reassignments

2

Medicare enrollment records show Theresa Thanh Nguyen reassigns Medicare billing to 2 organizations. Each organization bills Medicare for the services this provider delivers there; the nearest is listed first.

Theresa Thanh Ngoc Nguyen MD Inc
Same address
Internal Medicine
5030 WESTMINSTER AVE
Santa Ana, CA 92703
  • Reassigned Medicare billing, California enrollment
  • 3 clinicians in this Medicare group
NPI 1750667192 (714) 775-8090
Family Choice Aco Inc
3.5 mi
Internal Medicine
7631 WYOMING ST STE 201
Westminster, CA 92683
  • Reassigned Medicare billing, California enrollment
  • 75 clinicians in this Medicare group
NPI 1396416863 (714) 868-0765

Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

CLIA Laboratory Certificates CMS CLIA

Laboratory certificates issued under the Clinical Laboratory Improvement Amendments (CLIA) program, which sets federal quality standards for human laboratory testing in the United States. There is no official CMS crosswalk between CLIA and NPI numbers; these certificates are associated with this NPI by matching facility names, locations and phone numbers in the CMS CLIA registry.

Certificate of Waiver 05D0951274

Theresa Thanh Ngoc Nguyen, MD Inc · Santa Ana, CA
Active · expires Sep 14, 2028
CLIA Number05D0951274
Laboratory TypePhysician Office
Certificate Effective DateSeptember 15, 2026
Certificate Expiration DateSeptember 14, 2028
Laboratory DirectorThanh Nguyen MD
Laboratory Phone(714) 775-8090
Laboratory LocationTheresa Thanh Ngoc Nguyen, MD Inc5030 Westminster Ave, Santa Ana, CA 92703
CLIA data matches this NPI record on: Address Phone
This certificate is issued to a laboratory to perform only waived tests.

Areas of Expertise CMS Part B claims 11

Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.

Established patient office or other outpatient visit with low level od decision making, if using time, 20 minutes or more 99213
This is a routine visit for patients who have already been seen by the healthcare provider. During this approximately 20-29 minute appointment, your health status will be evaluated and any necessary treatments or tests will be discussed. It's a chance to address any health concerns you may have.
1,498 services403 patients
Insertion of needle into vein for collection of blood sample 36415
This procedure involves inserting a small needle into a vein, typically in your arm, to collect a blood sample. It's a quick and simple process to help diagnose or monitor health conditions. You may feel a small prick, but discomfort is minimal.
715 services324 patients
Chronic care management services, first 20 minutes of clinical staff time directed by health care professional, per calendar month 99490
Chronic care management services involve a healthcare professional directing clinical staff in managing your chronic conditions. This includes the first 20 minutes per month of services like medication management, care coordination, and health monitoring to help improve your health and quality of life.
504 services137 patients
Administration of influenza virus vaccine G0008
The administration of the influenza virus vaccine, also known as the flu shot, is a simple procedure to protect against the flu. A healthcare provider injects a small dose of the vaccine into your arm. This stimulates your immune system to produce antibodies, which will help your body fight off the flu if exposed.
206 services206 patients
Advance care planning, first 30 minutes 99497
Advance care planning is a process where you discuss your healthcare preferences with your doctor. This conversation, lasting up to 30 minutes, helps ensure your wishes are respected if you're unable to communicate them in the future. It's about your care, your way.
187 services187 patients
Annual wellness visit, includes a personalized prevention plan of service (pps), subsequent visit G0439
An annual wellness visit is a yearly appointment with your primary care provider to create or update a personalized prevention plan. This plan helps prevent illness based on your current health and risk factors. It's a subsequent visit, meaning it follows an initial assessment.
185 services185 patients

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 92703 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.

New Patient
$142.39 typical visit price
range $62.96 – $187.60
Typical copayment $35.59 (range $15.74 – $46.90)
Most-billed visit code 99204
Established Patient
$109.96 typical visit price
range $20.84 – $153.61
Typical copayment $27.49 (range $5.21 – $38.40)
Most-billed visit code 99214
Amounts reflect what Medicare beneficiaries in this ZIP area are typically charged for office visits. Patients with other coverage should check their individual plans.

Referred Medical Equipment & Supplies CMS DME claims 10

Durable medical equipment, devices and supplies this provider ordered from DME suppliers for patients, from Medicare fee-for-service claims.

Blood glucose test or reagent strips for home blood glucose monitor, per 50 strips A4253
DME-Other DME · category DE017N
31 suppliers154 claims285 services$4.19 avg. paid by Medicare
Lancets, per box of 100 A4259
DME-Medical/Surgical Supplies · category DA000N
27 suppliers114 claims118 services$0.76 avg. paid by Medicare
Walker, folding, wheeled, adjustable or fixed height E0143
DME-Other DME · category DE000N
4 suppliers11 claims11 services$28.95 avg. paid by Medicare
Transport chair, adult size, patient weight capacity up to and including 300 pounds E1038
DME-Other DME · category DE000N
2 suppliers23 claims24 services$5.49 avg. paid by Medicare
Albuterol, inhalation solution, fda-approved final product, non-compounded, administered through dme, unit dose, 1 mg J7613
DME-Drugs Administered Through DME · category DG006N
5 suppliers13 claims2,488 services$0.02 avg. paid by Medicare
Albuterol, up to 2.5 mg and ipratropium bromide, up to 0.5 mg, fda-approved final product, non-compounded, administered through dme J7620
DME-Drugs Administered Through DME · category DG006N
1 supplier12 claims1,440 services$0.09 avg. paid by Medicare
Dollar amounts are the average Medicare paid the supplier per service. They are not the cost to the patient.

Other Providers at the Same Location NPPES 3

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

TAM THI MINH NGUYEN
Nurse Practitioner (Women's Health)
5030 WESTMINSTER AVE
SANTA ANA, CA 92703
Orange County (714) 775-8090
THAI DINH NGUYEN M.D.
Internal Medicine
5030 WESTMINSTER AVE
SANTA ANA, CA 92703
Orange County (714) 775-8090
THERESA THANH NGOC NGUYEN MD INC
Internal Medicine
5030 WESTMINSTER AVE
SANTA ANA, CA 92703
Orange County (714) 775-8090

Frequently Asked Questions NPPES & CMS

Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.

What is Theresa Thanh Nguyen's NPI number?

The NPI number for Theresa Thanh Nguyen is 1003893801. It was assigned to this individual provider in the NPPES registry on December 22, 2005. The provider is also known as Thanh Ngoc Nguyen MD.

Where is Theresa Thanh Nguyen located?

Theresa Thanh Nguyen practices at 5030 Westminster Ave, Santa Ana, CA 92703. The listed phone number is (714) 775-8090.

What is Theresa Thanh Nguyen's specialty?

The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.

Is Theresa Thanh Nguyen enrolled in Medicare?

Yes. Theresa Thanh Nguyen is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.

Which organizations bill Medicare for Theresa Thanh Nguyen's services?

According to the CMS Revalidation Reassignment List (October 2026 release), Theresa Thanh Nguyen reassigns Medicare benefits to 2 organizations: Theresa Thanh Ngoc Nguyen MD Inc (Santa Ana, CA) and Family Choice Aco Inc (Westminster, CA). Each reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for Theresa Thanh Nguyen's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.

Does Theresa Thanh Nguyen hold a CLIA laboratory certificate?

Yes. A Certificate of Waiver (number 05D0951274) is associated with this NPI, valid through September 14, 2028. CLIA certificates authorize laboratory testing under the federal Clinical Laboratory Improvement Amendments program.

When was this NPI record last updated?

The NPPES record for Theresa Thanh Nguyen was last updated on July 20, 2026. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 3 months ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.