Katherine Tuan, M.D.
Internal Medicine Physician · Downey, CA
Katherine Tuan, M.D. is an internal medicine physician with a practice address in Downey, California, and NPI 1588907315, issued on Mar 29, 2013. Check the license (California A132432, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Katherine Tuan
- Credential
- M.D.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- A132432 CA
Self-reported in NPPES; status is on the state search - Practice location
- 9449 Imperial Hwy, Downey, CA 90242
- Phone
- (800) 823-4040
- Enumerated
- Mar 29, 2013
- Record last updated
- Nov 29, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20161024001293); accepts Medicare assignment
- Medical or professional school
- University Of Illinois College Of Med (Chi/Peor/Rock/Chm-Urb), 2013
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 9449 Imperial Hwy
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Sana Ashraf, MDPediatric Cardiology Physician1316177215
Verify Katherine Tuan in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A132432Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
34% more Medicare Part D claims than the average internal medicine physician in 2024
4,251 Medicare Part D claims for 393 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. 185 claims were for opioids.
Most prescribed
- Atorvastatin Calcium381 claims
- Amlodipine Besylate323 claims
- Losartan Potassium165 claims
- Lisinopril147 claims
- Levothyroxine Sodium137 claims
- Metformin Hcl129 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 GroupBellflower, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Katherine Tuan among 17,696 internal medicine physician records in California
Katherine Tuan, M.D. 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 2013, is newer than 71% of them.
- NPI issued2013 · 71% of these records are older, 26% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated2013 · 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).
114 internal medicine physician records list a practice address in Downey
They are 114 of the 3,607 NPPES records with a practice address in Downey, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Downey → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Sohail Afra, M.D.Downey, CA 902421023125176
- Ron Chai, M.D.Downey, CA 902421447361316
- Ronald Collins, M.D.Downey, CA 902421235176181
- Rashmi Desai, M.D.Downey, CA 902421801990247
- Basuki Gunawan, M.D.Downey, CA 902421346352473
- Danese Hayes, M.D.Downey, CA 902421689786733
- Goethe Hsu, M.D.Downey, CA 902421386656726
- Diana Hsu, M.D.Downey, CA 902421720090137
Common questions
What is Katherine Tuan, M.D.'s NPI number?
Katherine Tuan, M.D.'s National Provider Identifier (NPI) is 1588907315, issued on Mar 29, 2013. An NPI identifies a provider in billing; it is not a license.
Where is Katherine Tuan, M.D. located?
The NPPES record lists a practice address at 9449 Imperial Hwy, Downey, CA, 90242. Phone: (800) 823-4040. Providers update this record themselves, so call before visiting.
How can I verify Katherine Tuan, M.D.'s license?
NPPES lists California license number A132432, 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 Katherine Tuan, M.D. prescribe under Medicare Part D?
In 2024, Katherine Tuan, M.D. had 4,251 Medicare Part D claims for 393 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.