William Chao, MD
NPI 1841348661 · Emergency Medicine Physician · Baldwin Park, CA
Enrolled with Medicare as Practitioner - Emergency Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
William Chao, MD is a Emergency Medicine Physician provider in Baldwin Park, CA (NPI 1841348661).
Provider details
- NPI number
- 1841348661
- Entity type
- Individual
- Primary specialty
- Emergency Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- G78538 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
19 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
17 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) |
|---|---|---|
| Emergency Department Visit With Moderate Level of Medical Decision Making99284 | 17 | $122 |
Typical Medicare-allowed amounts for these services range $122–$122 (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 · 10 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Hydrocodone/Acetaminophenbrand: Hydrocodone-Acetaminophen | 45 | 45 |
| Cephalexin | 30 | 30 |
| Ondansetron Hcl | 25 | 25 |
| Amoxicillin/Potassium Clavbrand: Amoxicillin-Clavulanate Potass | 21 | 21 |
| Ibuprofen | 17 | 17 |
| Albuterol Sulfatebrand: Albuterol Sulfate Hfa | 14 | 14 |
| Ciprofloxacin Hcl |
Practice location
Mailing address
Registry dates
- Enumerated
- 2007-01-08
- Last updated
- 2021-11-30
Frequently asked questions
- What is William Chao's NPI number?
- William Chao's National Provider Identifier (NPI) is 1841348661, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is William Chao's specialty?
- William Chao is listed in the NPPES registry with a primary specialty of Emergency Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is William Chao located?
- William Chao's practice location on file with NPPES is 1011 Baldwin Park Blvd, Baldwin Park, CA 91706-5806.
- What is William Chao's phone number?
- The practice phone number listed in the NPPES registry for William Chao is (626) 851-1011.
- Does William Chao accept Medicare?
- William Chao is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is William Chao's NPI active?
- Yes — William Chao's NPI (1841348661) is active in the NPPES registry as of the last update on 2021-11-30.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.