WILLIAM J. RIESEN MD – NPI #1548377997
Internal Medicine

A physician who provides long-term, comprehensive care in the office and the hospital, managing both common and complex illness of adolescents, adults and the elderly. Internists are trained in the diagnosis and treatment of cancer, infections and diseases affecting the heart, blood, kidneys, joints and digestive, respiratory and vascular systems. They are also trained in the essentials of primary care internal medicine, which incorporates an understanding of disease prevention, wellness, substance abuse, mental health and effective treatment of common problems of the eyes, ears, skin, nervous system and reproductive organs.

Health Care Provider Taxonomy Code for Internal Medicine

WILLIAM RIESEN is a physician located in MASON CITY, IA. NPPES has assigned the NPI number 1548377997 to WILLIAM RIESEN on August 23, 2006. It is a Type-1 NPI, indicating this NPI number is associated with an individual. The primary taxonomy selected by this provider is 207R00000X from the Health Care Provider Taxonomy code set, which is classified as Internal Medicine.

The NPI profile was last updated on Jul 14, 2025. Use the NPI data found here to bill health insurance companies, identify providers enrolled in Medicare and Medicaid services or other HIPAA compliant transactions. See the complete NPI profile for WILLIAM RIESEN below.

NPI Profile for
WILLIAM J. RIESEN

NPI Number
1548377997
Enumeration Date

(about 20 years ago)
Entity Type
Type-1  Individual (Male)
Legal Name
WILLIAM J. RIESEN
Credentials
MD
Primary location
1010 4TH ST SW STE 305
MASON CITY, IA 50401-2801
Phone: (641) 428-5700 Fax: (641) 428-2515
Mailing address
621 S ILLINOIS AVE
SUITE 103
MASON CITY, IA 50401-5489
Phone: (641) 494-3041 Fax: (641) 494-3059
Sole Proprietor
No
Updated
Certification Date
Jul 14, 2025

Note: NPPES allows providers to attest to the accuracy of their NPI data. When a provider request any change to the NPI record, they will be able to attest to their changed NPI data, resulting in an updated certification date.

Identifiers

Identifiers for WILLIAM RIESEN

Identifiers are used to associate other provider identifiers such as Medicaid or other insurers (ie:, Blue Cross, Blue Shield, Aetna, Kaiser-Permanente, etc.), with their NPI number. These identifiers can be used in matching an NPI number to an insurer's records. However, not all providers have such numbers and not all providers choose to include them in their NPI information.

DescriptionIssuerStateIdentifier
otherWELLMARKIA46081
medicaidIA4137984
Taxonomy Code(s)

A taxonomy code is a code that describes the health care service provider's type, classification, and the area of specialization. The primary specialty for this provider is indicated as (Primary) below.

Taxonomy Classification / Specialization State License
207R00000X
- Internal Medicine (Primary)		 IA 31260

The taxonomy codes are selected by the provider at the time of NPI registration. Selection of a taxonomy code does not replace any credentialing or validation process that the provider requesting the code should complete.

Endpoint

Health Information Exchange (HEI)

HEI is the mobilization of health care information electronically across organizations within a region, community or hospital system. Endpoints provide a simple and secure way for participants to send authenticated, encrypted health information directly to known, trusted recipients over the internet such as primary care physicians, specialists, hospitals, labs, etc.

Endpoint
[email protected]
Endpoint type
Direct Messaging Address
Endpoint Description
MERCYONE NORTH IOWA DIRECT EMAIL
Content Type
OTHER
Affiliation
N
Endpoint Location
1010 4TH ST SW STE 305,
MASON CITY, IA 77025-1669

Additional Information

Education
PERELMAN SCHOOL OF MED AT THE UNIVERSITY OF PENNSYLVANIA - Graduated 1993
Accepts Medicare
This provider accepts Medicare-approved amount as payment in full. The Medicare-approved amount is the total the provider can be paid. When a provider accepts the Medicare-approved amount as payment, you won't be billed for more than the Medicare deductible & coinsureance.
Medicare Ordering & Referring
Provider can:
  • Refer to Part B
  • Order Durable Medical Equipment
  • Refer to Home Health Agency
  • Order Power Mobility Devices
Affiliations
WILLIAM RIESEN is affiliated with the following medical group(s):
  • HOSPITAL
    • HANCOCK COUNTY HEALTH SYSTEM
      532 1ST ST NW
      BRITT, IA 50423
    • MERCYONE NORTH IOWA MEDICAL CENTER
      1000 FOURTH STREET SW
      MASON CITY, IA 50401
    • UNIVERSITY OF IOWA HOSPITAL & CLINICS
      200 HAWKINS DRIVE
      IOWA CITY, IA 52242
  • HOME HEALTH AGENCY
    • CERRO GORDO COUNTY DEPARTMENT OF PUBLIC HEALTH
      2570 4TH ST SW SUITE 1
      MASON CITY, IA 50401
    • MERCYONE NORTH IOWA HOME CARE
      910 NORTH EISENHOWER
      MASON CITY, IA 50401
  • NURSING HOME
    • GOOD SHEPHERD HEALTH CENTER
      302 SECOND STREET NE
      MASON CITY, IA 50401
  • HOSPICE
    • MERCYONE NORTH IOWA HOSPICE
      232 SECOND STREET SE
      MASON CITY, IA 50401

Why is my NPI data (personal information) being displayed publicly?
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How do I correct or change the NPI data displayed here?
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Can I hide my NPI profile from the public?
Unfortunately, No. The NPPES discloses health care provider data under the Freedom of Information Act to the public, which means anyone may request such information directly from the National Plan & Provider Enumeration System. See the complete CMS Data Dissemination Notice here.