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

Nickolas S Demark, DO

Individual provider Hospitalist Physician · NPI 1114214004

Nickolas S Demark, DO practises Internal Medicine in Oskaloosa, Iowa. Graduated from Des Moines University of Osteopathic Medicine and Health Sciences in 2011, 15 years ago. Practices with Mahaska County Hospital, a 124-clinician group, works from 7 locations and accepts Medicare assignment. Licensed in Iowa, Michigan and Wisconsin.

Years since qualifying
15
Trained at
Des Moines University of Osteopathic Medicine and Health Sciences
Licensed in
IA, MI, WI
In the registry since
2011
Specialties on file
4
What do these letters mean?
DO — Doctor of Osteopathic Medicine
A fully licensed physician, trained like an MD with additional musculoskeletal training. Equivalent practice rights in all 50 states.

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Practice location Address checks out

1229 C Ave E
Oskaloosa, IA 52577-4246
Phone: (641) 672-3100
Fax: (641) 672-3381
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Additional practice locations (6)

  • 1818 N Meade St, Appleton, WI 54911-3454 — (920) 735-7645
  • 1715 Dousman St, Green Bay, WI 54303-3211 — (920) 496-4700
  • 1726 Shawano Ave, Green Bay, WI 54303-3216 — (920) 496-4700
  • 130 2nd St, Neenah, WI 54956-2883 — (920) 729-2738
  • 900 Illinois Ave, Stevens Point, WI 54481-3114 — (715) 346-5000
  • 900 Illinois Ave, Stevens Point, WI 54481-3114 — (715) 346-5000

Specialties & licences

Hospice and Palliative Medicine (Internal Medicine) Physician (primary) Taxonomy 207RH0002X · Licence DO-06639 (IA)
Hospitalist Physician Taxonomy 208M00000X · Licence 62482 (WI)
Internal Medicine Physician Taxonomy 207R00000X · Licence 62482 (WI)
Internal Medicine Physician Taxonomy 207R00000X · Licence 5101019580 (MI)

Record details

NPI number1114214004
Entity typeIndividual (Type 1)
GenderMale
Credentials DO
Sole proprietorNo
NPI enumeratedJune 30, 2011
Last updated in NPPESJuly 1, 2026
Certification dateJuly 1, 2026

Medicare enrollment

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

Medicare specialtyINTERNAL MEDICINE
Also practisesHOSPICE/PALLIATIVE CARE
Medical schoolDES MOINES UNIVERSITY OF OSTEOPATHIC MEDICINE AND HEALTH SCIENCES
Graduated 2011 (15 years in practice)
Group practice Mahaska County Hospital — 124 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

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 patients52
Services billed 54 a service is one billed item, such as a visit, a test or a procedure
Average patient age79

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 Mahaska County Hospital

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 124 clinicians in the practice; 12 are shown here.