Alex Tsai, DO
Emergency Medicine Physician · San Mateo, CA
Alex Tsai, DO is an emergency medicine physician with a practice address in San Mateo, California, and NPI 1114504321, issued on Mar 24, 2021. Check the license (California 20A21076, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Alex Tsai
- Credential
- DO
- Primary taxonomy
- Emergency Medicine Physician 207P00000X
- License number
- 20A21076 CA
Self-reported in NPPES; status is on the state search - Practice location
- 222 W 39TH Ave, San Mateo, CA 94403
- Phone
- (650) 573-2671
- Enumerated
- Mar 24, 2021
- Record last updated
- Sep 5, 2024
- Medicare enrollment
- Enrolled (PECOS I20230724003689); accepts Medicare assignment
- Medical or professional school
- Kansas City University Of Med & Biosciences, College Of Osteo Med, 2021
- Entity
- Type 1 · individual
8 nearest emergency medicine physician records → All 7,751 in California → Look up another NPI →
Also registered at 222 W 39TH Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- John Anderson, MDObstetrics & Gynecology Physician1013082429
- Shea AndersonClinical Social Worker1689964991
- Zohra Ansari, MSWClinical Social Worker1326462904
Verify Alex Tsai in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A21076Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
74% fewer Medicare Part D claims than the average emergency medicine physician in 2024
59 Medicare Part D claims for 48 beneficiaries, against an average of 226 among the 54,106 providers of this specialty who prescribed in Part D. Brand-name drugs were 0% of claims.
Most prescribed
- Cephalexin16 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.
Bills Medicare through one group practice
- Cep America - CaliforniaMountain View, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Alex Tsai among 7,751 emergency medicine physician records in California
Alex Tsai, DO is one of 7,751 emergency 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 2021, is newer than 92% of them.
- NPI issued2021 · 92% of these records are older, 5% newer
- In a Medicare fileYes · 81% of these records are
- In the CMS Doctors and Clinicians fileYes · 59% of these records are
- Graduated2021 · median 2011 among the 4,560 with a school on file
- Record last updated2024 · 59% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207P00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Emergency Medicine Physician providers in California
There are 7,751 emergency medicine physician records in California.
All 7,751 in California → Every provider in San Mateo → Emergency Medicine Physician nationwide →
The 8 emergency medicine physician records with the nearest ZIP codes
- Michael Aratow, M.D.San Mateo, CA 944031891804043
- Teri Chew, M.D.San Mateo, CA 944031508032905
- Dwight Gaggero, MDSan Mateo, CA 944031366433153
- Lawrence Gettler, MDSan Mateo, CA 944031083719926
- Edward Lipton, M.D.San Mateo, CA 944031770789604
- David Malmud, M.D.San Mateo, CA 944031619089281
- Kevin Masek, M.D.San Mateo, CA 944031811280563
- Zara Mathews, M.D.San Mateo, CA 944031124300652
Common questions
What is Alex Tsai, DO's NPI number?
Alex Tsai, DO's National Provider Identifier (NPI) is 1114504321, issued on Mar 24, 2021. An NPI identifies a provider in billing; it is not a license.
Where is Alex Tsai, DO located?
The NPPES record lists a practice address at 222 W 39TH Ave, San Mateo, CA, 94403. Phone: (650) 573-2671. Providers update this record themselves, so call before visiting.
How can I verify Alex Tsai, DO's license?
NPPES lists California license number 20A21076, 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 Alex Tsai, DO prescribe under Medicare Part D?
In 2024, Alex Tsai, DO had 59 Medicare Part D claims for 48 beneficiaries; the average among emergency medicine physician prescribers was 226. 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.