Eugene S. Ahn, MD
Radiation Oncology Physician · Simi Valley, CA
Eugene S. Ahn, MD is a radiation oncology physician with a practice address in Simi Valley, California, and NPI 1912999533, issued on Aug 19, 2005. Check the license (California A71690, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Eugene S. Ahn
- Credential
- MD
- Primary taxonomy
- Radiation Oncology Physician 2085R0001X
- License number
- A71690 CA
Self-reported in NPPES; status is on the state search - Practice location
- 2985 Sycamore Dr, Simi Valley, CA 93065
- Phone
- (805) 584-6611
- Enumerated
- Aug 19, 2005
- Record last updated
- Aug 5, 2022
- Fax
- (805) 584-0530
- Medicaid IDs
- 1912999533 CA
00A716900 CA - Medicare enrollment
- Enrolled (PECOS I20060502000475); accepts Medicare assignment
- Medical or professional school
- New York University School Of Medicine, 1998
- Entity
- Type 1 · individual
8 nearest radiation oncology physician records → All 735 in California → Look up another NPI →
Also registered at 2985 Sycamore Dr
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Ari Kassardjian, MDRadiation Oncology Physician1689200115
Verify Eugene S. Ahn in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A71690Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
54% fewer Medicare Part D claims than the average radiation oncology physician in 2024
61 Medicare Part D claims for 29 beneficiaries, against an average of 134 among the 4,851 providers of this specialty who prescribed in Part D.
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: $270.54
12 payments; by number, the most common kind was food and beverage; the largest payer was Sumitomo Pharma America, Inc. The 3,275 providers of this specialty with any payment received $1,897.85 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 2 group practices
- Adventist Health Physicians NetworkSimi Valley, CA
- Coastal Radiation Oncology Medical Group, Inc.Ventura, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Eugene S. Ahn among 735 radiation oncology physician records in California
Eugene S. Ahn, MD is one of 735 radiation oncology physician records with a practice address in California. 83% 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, 84% newer
- In a Medicare fileYes · 83% of these records are
- In the CMS Doctors and Clinicians fileYes · 74% of these records are
- Graduated1998 · median 2005 among the 545 with a school on file
- Record last updated2022 · 55% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 2085R0001X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Radiation Oncology Physician providers in California
There are 735 radiation oncology physician records in California.
All 735 in California → Every provider in Simi Valley → Radiation Oncology Physician nationwide →
The 8 radiation oncology physician records with the nearest ZIP codes
- Ari Kassardjian, MDSimi Valley, CA 930651689200115
- Robert Lum, M.D.Oxnard, CA 930361770589707
- Henry Montes, M.D.Oxnard, CA 930301215992193
- Timothy Oconnor, M.D.Oxnard, CA 930301982669396
- Lindsay Blount, M.D.Santa Barbara, CA 931051558417568
- George Cheng, M.D.Santa Barbara, CA 931051750437745
- Shane Cotter, M.D.Santa Barbara, CA 931051467643718
- Hyo Kim, M.D.Santa Barbara, CA 931051093752750
Common questions
What is Eugene S. Ahn, MD's NPI number?
Eugene S. Ahn, MD's National Provider Identifier (NPI) is 1912999533, issued on Aug 19, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Eugene S. Ahn, MD located?
The NPPES record lists a practice address at 2985 Sycamore Dr, Simi Valley, CA, 93065. Phone: (805) 584-6611. Providers update this record themselves, so call before visiting.
How can I verify Eugene S. Ahn, MD's license?
NPPES lists California license number A71690, 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 Eugene S. Ahn, MD prescribe under Medicare Part D?
In 2024, Eugene S. Ahn, MD had 61 Medicare Part D claims for 29 beneficiaries; the average among radiation oncology physician prescribers was 134. 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.