Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

Dr. Frederick Richard Stack, MD

Individual provider Internal Medicine Physician · NPI 1548256977

Dr. Frederick Richard Stack, MD practises Internal Medicine in Sioux City, Iowa. Graduated from University of Nebraska College of Medicine in 1991, 35 years ago. Practices with Benefis Hospitals Inc, a 398-clinician group, works from 4 locations and accepts Medicare assignment. Licensed in Arizona, Iowa and Montana.

Years since qualifying
35
Trained at
University of Nebraska College of Medicine
Licensed in
AZ, IA, MT
In the registry since
2005
Specialties on file
3
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

801 5th St
Sioux City, IA 51101-1326
Phone: (712) 279-2010
Fax: (712) 279-2034
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Additional practice locations (3)

  • 1821 N Trekell Rd, Casa Grande, AZ 85222-1705 — (520) 421-1122
  • 1 Medical Center Dr, Biddeford, ME 04005-9422 — (207) 283-7937
  • 1101 26th St S, Great Falls, MT 59405-5161 — (406) 455-4694

Specialties & licences

Internal Medicine Physician (primary) Taxonomy 207R00000X · Licence MD-46368 (IA)
Internal Medicine Physician Taxonomy 207R00000X · Licence 91977 (MT)
Specialist Taxonomy 174400000X · Licence 24459 (AZ)

Record details

NPI number1548256977
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorYes
NPI enumeratedSeptember 21, 2005
Last updated in NPPESJanuary 28, 2026
Certification dateJanuary 28, 2026

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyINTERNAL MEDICINE
Medical schoolUNIVERSITY OF NEBRASKA COLLEGE OF MEDICINE
Graduated 1991 (35 years in practice)
Group practice Benefis Hospitals Inc — 398 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations3 on file with Medicare

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients253
Services billed 676 a service is one billed item, such as a visit, a test or a procedure
Average patient age78

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at Benefis Hospitals Inc

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 398 clinicians in the practice; 12 are shown here.

Other providers in Sioux City