Frederick Stack, MD
NPI 1548256977 · Internal Medicine Physician · Sioux City, IA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Frederick Stack, MD is a Internal Medicine Physician provider in Sioux City, IA (NPI 1548256977).
Provider details
- NPI number
- 1548256977
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- Yes
- License
- 91977 (MT)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Other Service Providers
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
20 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
4 documented practice locations
- Medicare service volume (vs. specialty peers)28% of score
650 Medicare services, 2024 (ranked within specialty)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 35 Minutes99232 | 420 | $76 |
| Hospital Discharge Day Management, More Than 30 Minutes99239 | 122 | $111 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 44 | $166 |
| Initial Hospital Care With Straightforward Or Low-Level Medical Decision Making, If Using Time, at Least 55 Minutes99222 | 41 | $127 |
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 23 | $114 |
Typical Medicare-allowed amounts for these services range $76–$166 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 8 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Prednisone | 25 | 25 |
| Amlodipine Besylate | 13 | 13 |
| Amoxicillin/Potassium Clavbrand: Amoxicillin-Clavulanate Potass | 13 | 13 |
| Cefdinir | 12 | 12 |
| Atorvastatin Calcium | 11 | — |
| Clopidogrel Bisulfatebrand: Clopidogrel | 11 | — |
| Doxycycline Hyclate |
Practice location
Mailing address
Additional practice locations (3)
- 1821 N Trekell RdSuite 6Casa Grande, AZ 85222-1705Phone: (520) 421-1122Fax: (520) 421-0751
- 1 Medical Center DrBiddeford, ME 04005-9422Phone: (207) 283-7937
- 1101 26th St SGreat Falls, MT 59405-5161Phone: (406) 455-4694Fax: (406) 731-8318
Registry dates
- Enumerated
- 2005-09-21
- Last updated
- 2026-01-28
- Certified
- 2026-01-28
Frequently asked questions
- What is Frederick Stack's NPI number?
- Frederick Stack's National Provider Identifier (NPI) is 1548256977, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Frederick Stack's specialty?
- Frederick Stack is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Frederick Stack located?
- Frederick Stack's practice location on file with NPPES is 801 5th St, Sioux City, IA 51101-1326.
- What is Frederick Stack's phone number?
- The practice phone number listed in the NPPES registry for Frederick Stack is (712) 279-2010.
- Does Frederick Stack accept Medicare?
- Frederick Stack is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Frederick Stack's NPI active?
- Yes — Frederick Stack's NPI (1548256977) is active in the NPPES registry as of the last update on 2026-01-28.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.