Seiya Tokunaga, DO
Internal Medicine Physician · Oxnard, CA
Seiya Tokunaga, DO is an internal medicine physician with a practice address in Oxnard, California, and NPI 1629572334, issued on Mar 19, 2018. Check the license (California 20A17872, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Seiya Tokunaga
- Credential
- DO
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 20A17872 CA
Self-reported in NPPES; status is on the state search - Practice location
- 1600 N Rose Ave, Oxnard, CA 93030
- Phone
- (805) 988-2505
- Enumerated
- Mar 19, 2018
- Record last updated
- Nov 7, 2021 (not updated in 5 years: call before relying on the address or phone)
- Fax
- (805) 988-2502
- Medicare enrollment
- Enrolled (PECOS I20210806000891); accepts Medicare assignment
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 1600 N Rose Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Glen Abergel, M.D.Critical Care Medicine (Internal Medicine) Physician1093743924
- Waqas Aftab, M.D.Critical Care Medicine (Internal Medicine) Physician1043414220
- David Aguilar, M.D.Anesthesiology Physician1568484921
- Michelle AmparoRegistered Nurse1386593994
- Melissa Arbar, DOAnesthesiology Physician1063875136
- Sulaiman Barkho, MDInternal Medicine Physician1710417209
Verify Seiya Tokunaga in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A17872Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
97% fewer Medicare Part D claims than the average internal medicine physician in 2024
83 Medicare Part D claims for 30 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 27% of 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
- Socal HospitalistsLong Beach, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Seiya Tokunaga among 17,696 internal medicine physician records in California
Seiya Tokunaga, DO 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 2018, is newer than 84% of them.
- NPI issued2018 · 84% of these records are older, 14% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated2018 · 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).
44 internal medicine physician records list a practice address in Oxnard
They are 44 of the 3,211 NPPES records with a practice address in Oxnard, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Oxnard → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Charles Avery, M.D.Oxnard, CA 930301891735486
- Richard Brand, MDOxnard, CA 930301770527608
- Dorothea Clayton, M.D.Oxnard, CA 930301053596395
- Romany Demian, M.D.Oxnard, CA 930301043232085
- Shiu Man Lee, M.D.Oxnard, CA 930301144397555
- Bernard McDermott, D.O.Oxnard, CA 930301821101841
- Myo Min, M.DOxnard, CA 930301407176670
- Robert Nguyen, MDOxnard, CA 930301780775718
Common questions
What is Seiya Tokunaga, DO's NPI number?
Seiya Tokunaga, DO's National Provider Identifier (NPI) is 1629572334, issued on Mar 19, 2018. An NPI identifies a provider in billing; it is not a license.
Where is Seiya Tokunaga, DO located?
The NPPES record lists a practice address at 1600 N Rose Ave, Oxnard, CA, 93030. Phone: (805) 988-2505. Providers update this record themselves, so call before visiting.
How can I verify Seiya Tokunaga, DO's license?
NPPES lists California license number 20A17872, 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 Seiya Tokunaga, DO prescribe under Medicare Part D?
In 2024, Seiya Tokunaga, DO had 83 Medicare Part D claims for 30 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.