William Tsai, M.D.
NPI 1952356560 · Internal Medicine Physician · Irvine, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
William Tsai, M.D. is a Internal Medicine Physician provider in Irvine, CA (NPI 1952356560).
Provider details
- NPI number
- 1952356560
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- Yes
- License
- A71679 (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
2,165 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 Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 934 | $130 |
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 560 | $181 |
| Annual Wellness Visit, Includes a Personalized Prevention Plan of Service (pps), Subsequent VisitG0439 | 232 | $127 |
| Physician Or Allowed Practitioner Certification for Medicare-Covered Home Health Services Under a Home Health Plan of Care (patient Not Present), Including Contacts With Home Health Agency and Review of Reports of Patient Status Required By Physicians andG0180 | 201 | $54 |
| Residence Visit for Established Patient With High Level of Medical Decision Making, Per Day, If Using Time, at Least 60 Minutes99350 | 76 | $181 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 136 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Atorvastatin Calcium | 731 | 220 |
| Levothyroxine Sodium | 380 | 104 |
| Amlodipine Besylate | 376 | 104 |
| Zolpidem Tartrate | 288 | 71 |
| Losartan Potassium | 283 | 91 |
| Rosuvastatin Calcium | 276 | 79 |
| Metformin Hcl |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$182 across 4 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
- 2006-05-23
- Last updated
- 2010-07-16
Frequently asked questions
- What is William Tsai's NPI number?
- William Tsai's National Provider Identifier (NPI) is 1952356560, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is William Tsai's specialty?
- William Tsai is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is William Tsai located?
- William Tsai's practice location on file with NPPES is 19742 Macarthur Blvd, Irvine, CA 92612-2432.
- What is William Tsai's phone number?
- The practice phone number listed in the NPPES registry for William Tsai is (949) 955-0202.
- Does William Tsai accept Medicare?
- William Tsai is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is William Tsai's NPI active?
- Yes — William Tsai's NPI (1952356560) is active in the NPPES registry as of the last update on 2010-07-16.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.