Hai Nguyen, M.D.
NPI 1558516963 · Internal Medicine Physician · Santa Ana, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Hai Nguyen, M.D. is a Internal Medicine Physician provider in Santa Ana, CA (NPI 1558516963).
Provider details
- NPI number
- 1558516963
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- No
- License
- A114137 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
17 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
1,830 Medicare services, 2024 (ranked within specialty)
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 methodology.
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) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 35 Minutes99232 | 911 | $78 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 570 | $118 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 167 | $173 |
| Hospital Discharge Day Management, More Than 30 Minutes99239 | 132 | $115 |
| Critical Care, First 30-74 Minutes99291 | 50 | $211 |
Typical Medicare-allowed amounts for these services range $78–$211 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, not a price quote and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 31 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Pantoprazole Sodium | 68 | 66 |
| Cephalexin | 65 | 63 |
| Atorvastatin Calcium | 56 | 55 |
| Cefdinir | 53 | 52 |
| Metoprolol Tartrate | 50 | 46 |
| Prednisone | 49 | 46 |
| Furosemide | 40 | 37 |
Practice location
Mailing address
Registry dates
- Enumerated
- 2008-11-26
- Last updated
- 2013-12-19
Frequently asked questions
- What is Hai Nguyen's NPI number?
- Hai Nguyen's National Provider Identifier (NPI) is 1558516963, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Hai Nguyen's specialty?
- Hai Nguyen is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Hai Nguyen located?
- Hai Nguyen's practice location on file with NPPES is 2907 Sawgrass Dr, Santa Ana, CA 92706-1195.
- What is Hai Nguyen's phone number?
- The practice phone number listed in the NPPES registry for Hai Nguyen is (714) 675-3937.
- Does Hai Nguyen accept Medicare?
- Hai Nguyen is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Hai Nguyen's NPI active?
- Yes — Hai Nguyen's NPI (1558516963) is active in the NPPES registry as of the last update on 2013-12-19.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.