WILLIAM I PARKER MD
NPI 1356459903
Emergency Medicine in Mason City, IA
About William I Parker Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
WILLIAM I PARKER MD (NPI 1356459903) is an individual emergency medicine provider in Mason City, Iowa, licensed in Iowa (28723) 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 Other (1991).
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 2
Accepted 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
William I Parker 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.
Medicare Billing Reassignments
6Medicare enrollment records show William Parker reassigns Medicare billing to 6 organizations. Each organization bills Medicare for the services this provider delivers there; the nearest is listed first.
Mason City, IA 50401
- Reassigned Medicare billing, Iowa enrollment
- 420 clinicians in this Medicare group
Algona, IA 50511
- Reassigned Medicare billing, Iowa enrollment
- Also billed through NPI 1841361276 (Iowa)
- 27 clinicians in this Medicare group
Spirit Lake, IA 51360
- Reassigned Medicare billing, Iowa enrollment
- 65 clinicians in this Medicare group
Spencer, IA 51301
- Reassigned Medicare billing, Iowa enrollment
- 176 clinicians in this Medicare group
Tampa, FL 33609
- Reassigned Medicare billing, Florida enrollment
- 85 clinicians in this Medicare group
Aventura, FL 33180
- Reassigned Medicare billing, Florida enrollment
- 1,912 clinicians in this Medicare group
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 4
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.
Hospital Affiliations CMS Care Compare
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, IAPhysician 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.
Other Providers at the Same Location NPPES 20
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
MASON CITY, IA 50401
Frequently Asked Questions NPPES & CMS
Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.
What is William Parker's NPI number?
The NPI number for William Parker is 1356459903. It was assigned to this individual provider in the NPPES registry on August 25, 2006.
Where is William Parker located?
William Parker practices at 1000 4th St SW Suite ER, Mason City, IA 50401. The listed phone number is (641) 422-7234.
What is William Parker's specialty?
The primary specialty registered for this NPI is Emergency Medicine with taxonomy code 207P00000X.
Is William Parker enrolled in Medicare?
Yes. William Parker is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.
Which organizations bill Medicare for William Parker's services?
According to the CMS Revalidation Reassignment List (October 2026 release), William Parker reassigns Medicare benefits to 6 organizations: North Iowa Mercy Clinics (Mason City, IA), Kossuth Regional Health Center (Algona, IA), Lakes Regional Healthcare (Spirit Lake, IA), Spencer Municipal Hospital (Spencer, IA), Intensivist Medicine Services Of Fl, LLC (Tampa, FL) and 1 more organization, listed in the Medicare section above. Each reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for William Parker's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
What insurance does William Parker accept?
Health plans from Oscar Health, Oscar Health Maintenance Organization of Florida, Oscar Insurance Company and Wellmark Health Plan of Iowa, Inc. list William Parker as in-network in at least one marketplace plan. Coverage varies by plan and year; verify with the insurer or the provider before a visit.
Is William Parker affiliated with any hospitals?
According to CMS data, William Parker is affiliated with Mercyone North Iowa Medical Center.
When was this NPI record last updated?
The NPPES record for William Parker was last updated on October 11, 2023. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 3 years 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.
# William I Parker, MD · NPI 1356459903
Emergency Medicine physician in Mason City, Iowa. Individual provider, active in the CMS NPPES registry since August 25, 2006.
## Identity
- **NPI:** 1356459903 (Entity type: Individual)
- **Enumerated:** August 25, 2006
- **Primary specialty:** Emergency Medicine · taxonomy 207P00000X
- **State license:** 28723 (Iowa)
- **Sole proprietor:** No
## Practice location
- **Address:** 1000 4TH ST SW, SUITE ER, Mason City, IA 50401-2800
- **Phone:** (641) 422-7234 · **Fax:** (641) 422-6373
## Medicare
- **Medicare:** Enrolled (PECOS); accepts Medicare assignment
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Bills Medicare through:** 6 organizations under Medicare reassignment (form CMS-855R): North Iowa Mercy Clinics (NPI 1043321102, Mason City, IA); Kossuth Regional Health Center (NPI 1184636557, Algona, IA); Lakes Regional Healthcare (NPI 1609121896, Spirit Lake, IA); Spencer Municipal Hospital (NPI 1255328621, Spencer, IA); Intensivist Medicine Services Of Fl, LLC (NPI 1235836388, Tampa, FL); and 1 more · CMS Revalidation Reassignment List, October 2026 release
- **Medical school:** Other, class of 1991
## Record status
- **NPPES last updated:** October 11, 2023
- **Other identifiers:** Medicaid 2073189 (IA); Other 47792 (IA)
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Source: [NPI Profile](https://npiprofile.com/npi/1356459903) · Data from the CMS NPPES public registry.