William Lai, MD
NPI 1528180361 · Internal Medicine Physician · Fontana, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
William Lai, MD is a Internal Medicine Physician provider in Fontana, CA (NPI 1528180361).
Provider details
- NPI number
- 1528180361
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- Yes
- License
- A93123 (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
20 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) |
|---|---|---|
| Initial Hospital Care With Straightforward Or Low Level of Medical Decision Making, Per Day, If Using Time, at Least 40 Minutes99221 | 20 | $82 |
Typical Medicare-allowed amounts for these services range $82–$82 (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.
Practice location
Mailing address
Registry dates
- Enumerated
- 2007-04-04
- Last updated
- 2021-11-17
- Certified
- 2021-11-17
Frequently asked questions
- What is William Lai's NPI number?
- William Lai's National Provider Identifier (NPI) is 1528180361, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is William Lai's specialty?
- William Lai is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is William Lai located?
- William Lai's practice location on file with NPPES is 9961 Sierra Ave, Fontana, CA 92335-6720.
- What is William Lai's phone number?
- The practice phone number listed in the NPPES registry for William Lai is (909) 427-5000.
- Does William Lai accept Medicare?
- William Lai is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is William Lai's NPI active?
- Yes — William Lai's NPI (1528180361) is active in the NPPES registry as of the last update on 2021-11-17.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.