DR. WILLIAM J RIESEN MD
NPI 1548377997
Internal Medicine in Mason City, IA

Q: What is William Riesen's NPI number?

The NPI number for William Riesen is 1548377997. It was assigned to this individual provider in the NPPES registry on August 23, 2006.

Q: What is William Riesen's specialty?

The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.

Q: When was this NPI record last updated?

The NPPES record for William Riesen was last updated on July 14, 2025. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 15 months ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.

Active since August 23, 2006PECOS EnrolledAccepts Medicare Assignment

1010 4TH ST SW STE 305, MASON CITY, IA 50401(641) 428-5700(641) 428-2515 Get Directions Write a Review

NPPES record last updated: July 14, 2025. Verified against the NPPES registry weekly; last sync: October 18, 2026.

Record update history: Aug 11, 2022, Aug 5, 2022, Apr 20, 2021 and 1 more (4 updates tracked since 2020).

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About Dr. William J Riesen Md NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

DR. WILLIAM J RIESEN MD (NPI 1548377997) is an individual internal medicine provider in Mason City, Iowa, licensed in Iowa (31260) and active in the NPI registry since August 2006. He is enrolled in Medicare PECOS, is affiliated with Mercyone North Iowa Medical Center, and is a graduate of Perelman School Of Med At The University Of Pennsylvania (1993).

NPPES Registry Identity

NPI1548377997

Entity TypeIndividualMale

Primary Taxonomy207R00000X

Provider Legal NameDR. WILLIAM J RIESENCredential: MD

Location Address1010 4TH ST SW STE 305Mason City, IA 50401-2801

Mailing Address621 S Illinois Ave, Suite 103Mason City, IA 50401-5489 · (641) 494-3041 · Fax (641) 494-3059

Phone(641) 428-5700

Fax(641) 428-2515

Sole ProprietorNo

Medical School CMSPerelman School Of Med At The University Of PennsylvaniaGraduated 1993

Enumeration DateAugust 23, 2006

Last NPPES UpdateJuly 14, 20254 updates tracked since enumeration

NPPES CertifiedJuly 14, 2025

✔ NPI 1548377997 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyInternal MedicineAllopathic & Osteopathic Physicians

Taxonomy Code207R00000X

License✔ Licensed in IA · 31260

Definition

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.

1010 4TH ST SW STE 305, Mason City, IA 50401

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Other Identifiers 2

Medicaid4137984IA

Other46081IA · Wellmark

Accepted Insurance

The full list of accepted plans is on the Insurance tab. Issuers include Ambetter from NH Healthy Families, Ambetter from Sunflower Health Plan, Ambetter Health and more.Insurance ›

Medicare Participation & PECOS CMS

Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.

Medicare Enrollment Status

✔

Enrolled in Medicare and accepts Medicare assignment

Dr. William J Riesen Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.

PECOS PAC ID8921146341

PECOS Enrollment IDI20091105000048

Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Medicare Billing Reassignment

Medicare enrollment records show William Riesen reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.

North Iowa Mercy Clinics

Same address

Obstetrics & Gynecology

1010 4TH ST SW STE 220
Mason City, IA 50401

Reassigned Medicare billing, Iowa enrollment
420 clinicians in this Medicare group

NPI 1306857347 (641) 428-5100

Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

Areas of Expertise CMS Part B claims 10

Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.

Routine electrocardiogram (ecg) using at least 12 leads with interpretation and report only 93010

A routine electrocardiogram (ECG) with 12 leads is a simple, non-invasive test that records the electrical activity of your heart. It helps in identifying heart conditions by detecting irregularities in your heart rhythms. The results are interpreted and a report is provided.

1,895 services1,376 patients

Established patient office or other outpatient visit with low level od decision making, if using time, 20 minutes or more 99213

This is a routine visit for patients who have already been seen by the healthcare provider. During this approximately 20-29 minute appointment, your health status will be evaluated and any necessary treatments or tests will be discussed. It's a chance to address any health concerns you may have.

641 services360 patients

Established patient office or other outpatient visit with moderate level of decision making, if using time, 30 minutes or more 99214

This is a routine check-up for patients who have previously visited our clinic. It involves a comprehensive review of your health and any ongoing treatments. The consultation lasts between 30-39 minutes, allowing enough time to discuss any concerns.

527 services312 patients

Subsequent hospital care with moderate levelof medical decision making, if using time, at least 35 minutes 99232

Follow-up hospital inpatient care involves daily check-ups while you're admitted in the hospital. Typically, a healthcare provider spends about 25 minutes each day reviewing your condition, adjusting treatment if needed, and answering any questions you might have.

182 services30 patients

Annual wellness visit, includes a personalized prevention plan of service (pps), subsequent visit G0439

An annual wellness visit is a yearly appointment with your primary care provider to create or update a personalized prevention plan. This plan helps prevent illness based on your current health and risk factors. It's a subsequent visit, meaning it follows an initial assessment.

175 services175 patients

Hospital discharge day management, 30 minutes or less 99238

Hospital discharge day management of 30 minutes or less includes finalizing your treatment, discussing your progress, and planning after-care at home. It ensures you're ready to leave the hospital and continue recovery safely.

46 services31 patients

Hospital Affiliations CMS Care Compare 4

Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.

Mercyone North Iowa Medical Center

Acute Care Hospitals · Mason City, IA

3/5 CMS rating

OwnershipVoluntary non-profit - Private

CMS Certification Number160064

Location1000 Fourth Street SWMason City, IA 50401 · Cerro Gordo County

Emergency services Birthing friendly

Mercyone Des Moines Medical Center

Acute Care Hospitals · Des Moines, IA

3/5 CMS rating

OwnershipVoluntary non-profit - Private

CMS Certification Number160083

Location1111 6th AveDes Moines, IA 50314 · Polk County

Emergency services Birthing friendly

Iowa Specialty Hospital - Belmond

Critical Access Hospitals · Belmond, IA

OwnershipGovernment - Local

CMS Certification Number161301

Location403 First Street SEBelmond, IA 50421 · Wright County

Emergency services

Franklin General Hospital

Critical Access Hospitals · Hampton, IA

OwnershipGovernment - Local

CMS Certification Number161308

Location1720 Central Avenue EastHampton, IA 50441 · Franklin County

Emergency services

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 50401 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.

New Patient

$122.23 typical visit price

range $52.96 – $161.40

Typical copayment $30.55 (range $13.24 – $40.35)

Most-billed visit code 99204

Established Patient

$94.05 typical visit price

range $16.91 – $131.98

Typical copayment $23.51 (range $4.22 – $32.99)

Most-billed visit code 99214

Amounts reflect what Medicare beneficiaries in this ZIP area are typically charged for office visits. Patients with other coverage should check their individual plans.

Referred Medical Equipment & Supplies CMS DME claims 12

Durable medical equipment, devices and supplies this provider ordered from DME suppliers for patients, from Medicare fee-for-service claims.

Sterile water/saline, 500 ml A4217

DME-Medical/Surgical Supplies · category DA000N

1 supplier17 claims122 services$2.98 avg. paid by Medicare

Blood glucose test or reagent strips for home blood glucose monitor, per 50 strips A4253

DME-Other DME · category DE017N

13 suppliers65 claims141 services$5.44 avg. paid by Medicare

Lancets, per box of 100 A4259

DME-Medical/Surgical Supplies · category DA000N

10 suppliers34 claims45 services$0.96 avg. paid by Medicare

Tubing with integrated heating element for use with positive airway pressure device A4604

DME-Other DME · category DE001N

5 suppliers16 claims16 services$45.89 avg. paid by Medicare

Full face mask used with positive airway pressure device, each A7030

DME-Other DME · category DE001N

2 suppliers11 claims11 services$108.95 avg. paid by Medicare

Cushion for use on nasal mask interface, replacement only, each A7032

DME-Other DME · category DE001N

5 suppliers20 claims86 services$23.82 avg. paid by Medicare

Dollar amounts are the average Medicare paid the supplier per service. They are not the cost to the patient.

Other Providers at the Same Location NPPES 15

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

GABRIEL UNKRICH DO

Student in an Organized Health Care Education/Training Program