John Byron Williams, M.D.
Gastroenterology Physician · Madison, WI
John Byron Williams, M.D. is a gastroenterology physician with a practice address in Madison, Wisconsin, and NPI 1265516421, issued on Oct 24, 2006. Check the license (Wisconsin 43694-020, as entered in NPPES) on the Wisconsin Medical Examining Board; the Medicare figures below come from public CMS files.
- Name
- John Byron Williams
- Credential
- M.D.
- Primary taxonomy
- Gastroenterology Physician 207RG0100X
- License number
- 43694-020 WI
Self-reported in NPPES; status is on the state search - Practice location
- 20 S Park St, Madison, WI 53715
- Phone
- (608) 287-2680
- Enumerated
- Oct 24, 2006
- Record last updated
- Jan 27, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20070814000788); accepts Medicare assignment
- Medical or professional school
- Saint Louis University School Of Medicine, 2000
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest gastroenterology physician records → All 340 in Wisconsin → Look up another NPI →
Also registered at 20 S Park St
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Eliza Bennett, M.D.Obstetrics & Gynecology Physician1003852161
- Stephen Bernsten, MDPlastic Surgery Physician1114989043
Verify John Byron Williams in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWisconsin Medical Examining Board
Search for license 43694-020Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
16% fewer Medicare Part D claims than the average gastroenterology physician in 2024
681 Medicare Part D claims for 362 beneficiaries, against an average of 811 among the 16,445 providers of this specialty who prescribed in Part D. Brand-name drugs were 18% of claims.
Most prescribed
- Gavilyte-C271 claims
- Omeprazole70 claims
- Famotidine33 claims
- Mesalamine29 claims
- Balsalazide Disodium28 claims
- Humira(Cf) Pen25 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
- University OF Wisconsin Medical Foundation IncMadison, WI
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
John Byron Williams among 340 gastroenterology physician records in Wisconsin
John Byron Williams, M.D. 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 fileYes · 70% of these records are
- Graduated2000 · median 2003 among the 239 with a school on file
- Record last updated2021 · 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 Madison → Gastroenterology Physician nationwide →
The 8 gastroenterology physician records with the nearest ZIP codes
- Michael Allan, MDMadison, WI 537151558300822
- Siobhan Byrne, M.D.Madison, WI 537151417915836
- Abigail Christiansen, MDMadison, WI 537151427003227
- Sigurdur Einarsson, MDMadison, WI 537151245206317
- Jason Gonzaga, M.D.Madison, WI 537151710026430
- Gary Griglione, MDMadison, WI 537151013931203
- John Hamilton, MDMadison, WI 537151659310969
- Susan Lepinski, MDMadison, WI 537151780650713
Common questions
What is John Byron Williams, M.D.'s NPI number?
John Byron Williams, M.D.'s National Provider Identifier (NPI) is 1265516421, issued on Oct 24, 2006. An NPI identifies a provider in billing; it is not a license.
Where is John Byron Williams, M.D. located?
The NPPES record lists a practice address at 20 S Park St, Madison, WI, 53715. Phone: (608) 287-2680. Providers update this record themselves, so call before visiting.
How can I verify John Byron Williams, M.D.'s license?
NPPES lists Wisconsin license number 43694-020, 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 John Byron Williams, M.D. prescribe under Medicare Part D?
In 2024, John Byron Williams, M.D. had 681 Medicare Part D claims for 362 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.