William J. Riesen, MD
Internal Medicine Physician · Mason City, IA
William J. Riesen, MD is an internal medicine physician with a practice address in Mason City, Iowa, and NPI 1548377997, issued on Aug 23, 2006. Check the license (Iowa 31260, as entered in NPPES) on the Iowa Board of Medicine; the Medicare figures below come from public CMS files.
- Name
- William J. Riesen
- Credential
- MD
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 31260 IA
Self-reported in NPPES; status is on the state search - Practice location
- 1010 4TH St SW Ste 305, Mason City, IA 50401
- Phone
- (641) 428-5700
- Enumerated
- Aug 23, 2006
- Record last updated
- Jul 14, 2025
- Fax
- (641) 428-2515
- Medicaid ID
- 4137984 IA
- Medicare enrollment
- Enrolled (PECOS I20091105000048); accepts Medicare assignment
- Medical or professional school
- Perelman School Of Med At The University Of Pennsylvania, 1993
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 871 in Iowa → Look up another NPI →
Also registered at 1010 4TH St SW Ste 305
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Spencer Boster, DOStudent in an Organized Health Care Education/Training Program1639973332
- Luke Carlson, MDInternal Medicine Physician1457092165
- Celine Durgin, MDStudent in an Organized Health Care Education/Training Program1396488953
- Linda Floden, MDFamily Medicine Physician1467563452
- Matthew Hardee, D.O.Internal Medicine Physician1548408867
Verify William J. Riesen in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersIowa Board of Medicine
Search for license 31260Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
2.3 times the Medicare Part D claims of the average internal medicine physician in 2024
7,306 Medicare Part D claims for 581 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. Brand-name drugs were 12% of claims. 200 claims were for opioids.
Most prescribed
- Atorvastatin Calcium435 claims
- Levothyroxine Sodium283 claims
- Lisinopril270 claims
- Losartan Potassium266 claims
- Omeprazole233 claims
- Eliquis225 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
- North Iowa Mercy ClinicsMason City, IA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
William J. Riesen among 871 internal medicine physician records in Iowa
William J. Riesen, MD is one of 871 internal medicine physician records with a practice address in Iowa. 70% 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 11% of them.
- NPI issued2006 · 11% of these records are older, 62% newer
- In a Medicare fileYes · 70% of these records are
- In the CMS Doctors and Clinicians fileYes · 44% of these records are
- Graduated1993 · median 2008 among the 386 with a school on file
- Record last updated2025 · 46% 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 Iowa practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
36 internal medicine physician records list a practice address in Mason City
They are 36 of the 866 NPPES records with a practice address in Mason City, and 871 internal medicine physician records in Iowa.
All 871 in Iowa → Every provider in Mason City → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Phillip Alscher, MDMason City, IA 504011700993888
- Vaughan Cipperly, MDMason City, IA 504011942235429
- Patrick Dunlay, DOMason City, IA 504011811004294
- Melissa Frame, MDMason City, IA 504011881796712
- Bruce Harlan, MDMason City, IA 504011336256593
- Mark Johnson, MDMason City, IA 504011013923127
- Janice Kirsch, MDMason City, IA 504011992809636
- Ali Mardan, PHD, MD, RPVI, FACPMason City, IA 504011619905353
Common questions
What is William J. Riesen, MD's NPI number?
William J. Riesen, MD's National Provider Identifier (NPI) is 1548377997, issued on Aug 23, 2006. An NPI identifies a provider in billing; it is not a license.
Where is William J. Riesen, MD located?
The NPPES record lists a practice address at 1010 4TH St SW Ste 305, Mason City, IA, 50401. Phone: (641) 428-5700. Providers update this record themselves, so call before visiting.
How can I verify William J. Riesen, MD's license?
NPPES lists Iowa license number 31260, as entered by the provider. Search the Iowa Board of Medicine at https://dial.iowa.gov/about-dial/boards-and-commissions/medicine. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does William J. Riesen, MD prescribe under Medicare Part D?
In 2024, William J. Riesen, MD had 7,306 Medicare Part D claims for 581 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.