Warren Hsiao, MD
Internal Medicine Physician · Harbor City, CA
Warren Hsiao, MD is an internal medicine physician with a practice address in Harbor City, California, and NPI 1316095391, issued on Jan 8, 2007. Check the license (California A55179, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Warren Hsiao
- Credential
- MD
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- A55179 CA
Self-reported in NPPES; status is on the state search - Practice location
- 25825 Vermont Ave, Harbor City, CA 90710
- Phone
- (310) 325-5111
- Enumerated
- Jan 8, 2007
- Record last updated
- Nov 18, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20100621000218); accepts Medicare assignment
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 25825 Vermont Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Warren Hsiao in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A55179Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
2.5 times the Medicare Part D claims of the average internal medicine physician in 2024
7,997 Medicare Part D claims for 782 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 10% of claims.
Most prescribed
- Atorvastatin Calcium656 claims
- Rosuvastatin Calcium645 claims
- Amlodipine Besylate526 claims
- Losartan Potassium385 claims
- Lisinopril274 claims
- Levothyroxine Sodium212 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
- Southern California Permanente Medical GroupTorrance, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Warren Hsiao among 17,696 internal medicine physician records in California
Warren Hsiao, MD is one of 17,696 internal medicine physician records with a practice address in California. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2007, is newer than 44% of them.
- NPI issued2007 · 44% of these records are older, 44% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated1994 · median 2004 among the 11,065 with a school on file
- Record last updated2021 · 61% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
64 internal medicine physician records list a practice address in Harbor City
They are 64 of the 958 NPPES records with a practice address in Harbor City, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Harbor City → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Rafael AmaroHarbor City, CA 907101750475661
- Jennifer Armstrong, MDHarbor City, CA 907101578567178
- Sook Chung, M.D.Harbor City, CA 907101306824487
- Margaret David, MDHarbor City, CA 907101336216209
- William Fleury, MDHarbor City, CA 907101912078825
- Roger Hartman, MDHarbor City, CA 907101083781942
- Ryokei Imai, MDHarbor City, CA 907101003975608
- Veassa Johnson, M.DHarbor City, CA 907101346308756
Common questions
What is Warren Hsiao, MD's NPI number?
Warren Hsiao, MD's National Provider Identifier (NPI) is 1316095391, issued on Jan 8, 2007. An NPI identifies a provider in billing; it is not a license.
Where is Warren Hsiao, MD located?
The NPPES record lists a practice address at 25825 Vermont Ave, Harbor City, CA, 90710. Phone: (310) 325-5111. Providers update this record themselves, so call before visiting.
How can I verify Warren Hsiao, MD's license?
NPPES lists California license number A55179, 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 Warren Hsiao, MD prescribe under Medicare Part D?
In 2024, Warren Hsiao, MD had 7,997 Medicare Part D claims for 782 beneficiaries; the average among internal medicine physician prescribers was 3,176. 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.