William Tsai, D.O.
Family Medicine Physician · Upland, CA
William Tsai, D.O. is a family medicine physician with a practice address in Upland, California, and NPI 1285620443, issued on Sep 23, 2005. Check the license (California 20A7115, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- William Tsai
- Credential
- D.O.
- Primary taxonomy
- Family Medicine Physician 207Q00000X
- License number
- 20A7115 CA
Self-reported in NPPES; status is on the state search - Practice location
- 510 N 13TH Ave Ste 101, Upland, CA 91786
- Phone
- (909) 985-8838
- Enumerated
- Sep 23, 2005
- Record last updated
- Apr 24, 2024
- Fax
- (909) 985-8899
- Medicaid ID
- 00AX71150 CA
- Medicare enrollment
- Enrolled (PECOS I20031230000277); accepts Medicare assignment
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest family medicine physician records → All 17,133 in California → Look up another NPI →
Verify William Tsai in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A7115Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
2.9 times the Medicare Part D claims of the average family medicine physician in 2024
10,223 Medicare Part D claims for 506 beneficiaries, against an average of 3,544 among the 117,163 providers of this specialty who prescribed in Part D. Brand-name drugs were 13% of claims. 270 claims were for opioids.
Most prescribed
- Atorvastatin Calcium805 claims
- Amlodipine Besylate533 claims
- Levothyroxine Sodium391 claims
- Losartan Potassium367 claims
- Metformin Hcl288 claims
- Trazodone Hcl234 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Industry payments in 2024: $1,291.06
52 payments; by number, the most common kind was food and beverage; the largest payer was Novartis Pharmaceuticals Corporation. The 55,478 providers of this specialty with any payment received $902.55 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through one group practice
- William Tsai, D.O., IncUpland, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
William Tsai among 17,133 family medicine physician records in California
William Tsai, D.O. is one of 17,133 family medicine physician records with a practice address in California. 81% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 94% newer
- In a Medicare fileYes · 81% of these records are
- In the CMS Doctors and Clinicians fileYes · 62% of these records are
- Graduated1996 · median 2005 among the 10,652 with a school on file
- Record last updated2024 · 58% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207Q00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
38 family medicine physician records list a practice address in Upland
They are 38 of the 1,846 NPPES records with a practice address in Upland, and 17,133 family medicine physician records in California.
All 17,133 in California → Every provider in Upland → Family Medicine Physician nationwide →
The 8 family medicine physician records with the nearest ZIP codes
- Richard Armour, D.OUpland, CA 917861366488215
- Louis Brenner, M.D.Upland, CA 917861003852815
- Bryan Chan, MDUpland, CA 917861417059957
- Louis Dibernardo, MDUpland, CA 917861528045358
- Warren Regh Gabrillo, M.D.Upland, CA 917861982689295
- Dwight Guan, MDUpland, CA 917861184644676
- Rick Hirsch, D.O.Upland, CA 917861497774954
- James Ho, MDUpland, CA 917861669440988
Common questions
What is William Tsai, D.O.'s NPI number?
William Tsai, D.O.'s National Provider Identifier (NPI) is 1285620443, issued on Sep 23, 2005. An NPI identifies a provider in billing; it is not a license.
Where is William Tsai, D.O. located?
The NPPES record lists a practice address at 510 N 13TH Ave Ste 101, Upland, CA, 91786. Phone: (909) 985-8838. Providers update this record themselves, so call before visiting.
How can I verify William Tsai, D.O.'s license?
NPPES lists California license number 20A7115, as entered by the provider. Search the Medical Board of California at https://www.mbc.ca.gov/License-Verification/default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does William Tsai, D.O. prescribe under Medicare Part D?
In 2024, William Tsai, D.O. had 10,223 Medicare Part D claims for 506 beneficiaries; the average among family medicine physician prescribers was 3,544. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.