Gregory A. Derfus, MD
Gastroenterology Physician · Eau Claire, WI
Gregory A. Derfus, MD is a gastroenterology physician with a practice address in Eau Claire, Wisconsin, and NPI 1861465304, issued on Feb 7, 2006. Check the license (Wisconsin 28466, as entered in NPPES) on the Wisconsin Medical Examining Board; the Medicare figures below come from public CMS files.
- Name
- Gregory A. Derfus
- Credential
- MD
- Primary taxonomy
- Gastroenterology Physician 207RG0100X
- License number
- 28466 WI
Self-reported in NPPES; status is on the state search - Practice location
- 1400 Bellinger St, Eau Claire, WI 54703
- Phone
- (715) 838-5222
- Enumerated
- Feb 7, 2006
- Record last updated
- Feb 9, 2024
- Entity
- Type 1 · individual
8 nearest gastroenterology physician records → All 340 in Wisconsin → Look up another NPI →
Also registered at 1400 Bellinger St
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Gregory A. Derfus in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWisconsin Medical Examining Board
Search for license 28466Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
96% fewer Medicare Part D claims than the average gastroenterology physician in 2024
30 Medicare Part D claims for 15 beneficiaries, against an average of 811 among the 16,445 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.
Gregory A. Derfus among 340 gastroenterology physician records in Wisconsin
Gregory A. Derfus, MD is one of 340 gastroenterology physician records with a practice address in Wisconsin. 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 2006, is newer than 7% of them.
- NPI issued2006 · 7% of these records are older, 44% newer
- In a Medicare fileYes · 83% of these records are
- In the CMS Doctors and Clinicians fileNo · 70% of these records are
- Record last updated2024 · 52% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RG0100X and a Wisconsin practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Gastroenterology Physician providers in Wisconsin
There are 340 gastroenterology physician records in Wisconsin.
All 340 in Wisconsin → Every provider in Eau Claire → Gastroenterology Physician nationwide →
The 8 gastroenterology physician records with the nearest ZIP codes
- Mainor Antillon-Galdamez, M.D.Eau Claire, WI 547031215962873
- Victor Arce Gutierrez, MDEau Claire, WI 547031659876969
- Victor Ciofoaia, M.D.Eau Claire, WI 547031174851273
- Jeffrey Hubers, M.D.Eau Claire, WI 547031750648820
- Christian Mendez, MDEau Claire, WI 547031528051554
- Daniel Penrice, MDEau Claire, WI 547031235626045
- Nadim Salfiti, MDEau Claire, WI 547031194879262
- Maria Samuel, MDEau Claire, WI 547031417274218
Common questions
What is Gregory A. Derfus, MD's NPI number?
Gregory A. Derfus, MD's National Provider Identifier (NPI) is 1861465304, issued on Feb 7, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Gregory A. Derfus, MD located?
The NPPES record lists a practice address at 1400 Bellinger St, Eau Claire, WI, 54703. Phone: (715) 838-5222. Providers update this record themselves, so call before visiting.
How can I verify Gregory A. Derfus, MD's license?
NPPES lists Wisconsin license number 28466, as entered by the provider. Search the Wisconsin Medical Examining Board at https://dsps.wi.gov/Pages/BoardsCouncils/MEB/Default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Gregory A. Derfus, MD prescribe under Medicare Part D?
In 2024, Gregory A. Derfus, MD had 30 Medicare Part D claims for 15 beneficiaries; the average among gastroenterology physician prescribers was 811. 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.