2026 NPPES data Internal Medicine Physician NPI 1063400620 MD
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THERESA BRENNAN, MD

Internal Medicine Physician in IOWA CITY, Iowa. CMS National Plan and Provider Enumeration System profile including specialty classification, practice address, and Medicare prescribing data when reported.

Federal data — no proprietary rating. PlainDoctor publishes the actual CMS NPPES and Medicare records — NPI registration, specialty, practice location, and prescribing data — without a composite score or editorial opinion on top. Every field traces to a federal source.
Prescribing volume
959
Medicare Part D claims · 109 beneficiaries · Internal Medicine Physician avg: 3K
Generic prescribing
91%
generic claims · 9% brand-name · higher generic rates reduce patient out-of-pocket costs

What the federal data shows

THERESA BRENNAN, MD filed 959 Medicare Part D claims in 2023 as a Internal Medicine Physician in IOWA CITY, Iowa, prescribing 91% generic.

959
Part D claims, 2023
91%
generic prescribing
Likely
board-certified (heuristic)

Every figure on this page comes straight from federal CMS records (NPPES, Medicare Part D, MIPS, Open Payments) — no proprietary rating or editorial opinion is applied.

THERESA BRENNAN, MD's Medicare Part D volume vs every U.S. prescriber

Total Medicare Part D claims, 2023 — across all CMS prescribers nationally

959 Top 25% higher than 75% of 1,370,886 prescribers

0–200: 670,926 prescribers (49%). Below this entry. 200–400: 182,923 prescribers (13%). Below this entry. 400–600: 90,619 prescribers (7%). Below this entry. 600–800: 56,224 prescribers (4%). Below this entry. 800–1,000: 40,919 prescribers (3%). This entry sits in this band. 1,000–1,200: 31,827 prescribers (2%). Above this entry. 1,200–1,400: 26,224 prescribers (2%). Above this entry. 1,400–1,600: 21,710 prescribers (2%). Above this entry. 1,600–1,800: 19,072 prescribers (1%). Above this entry. 1,800–2,000: 16,451 prescribers (1%). Above this entry. 2,000–2,200: 213,991 prescribers (16%). Above this entry. This provider 0 2K+ every Part D prescriber (claims/yr), bucketed by value

Each bar is a band; taller bars hold more prescribers. The dashed line + filled bar mark this entry. Hover or tap any bar for its full count, share, and where it sits relative to this entry.

Source CMS Medicare Part D Prescriber Public Use File · 2023

Board certification likely (heuristic — not verified)

THERESA BRENNAN, MD practices in an ABMS-board-eligible specialty and shows active CMS Medicare participation + 1 hospital affiliation — signals consistent with board-certified status. For verified board certification, see CertificationMatters.org (the official ABMS public lookup).

What does the federal data show about THERESA BRENNAN, MD?

Quality data not reported

NPI registry status

Active

Issued 10/07/2005

NPI 1063400620

Primary specialty

Internal Medicine Physician

High-volume

172,858 US NPIs in this specialty

Medicare Part D claims

959 65% vs specialty avg

2023 prescription claims

Specialty avg: 2,716

Specialty distribution in Iowa

How Internal Medicine Physician compares to other specialties among Iowa providers

Iowa providers

Internal Medicine Physician share within Iowa

1. Internal Medicine Physician42%2. Internal medicine21%3. Family medicine17%4. Surgical12%5. Pediatric8%
Internal Medicine Physician share within Iowa

Specialty board-certification context

Estimated specialty board-certified rate — Internal Medicine Physician (ABMS / AOA reference)

Quality data not reported
Est. board-certified rate
78%
Internal Medicine Physician ABMS/AOA estimate

Est. board-certified rate (Internal Medicine Physician) — ABMS / AOA estimate

0%100%78%
Est. board-certified rate (Internal Medicine Physician) — ABMS / AOA estimate

The Merit-based Incentive Payment System (MIPS) scores providers 0–100 across four performance categories: Quality, Cost, Promoting Interoperability, and Improvement Activities, weighted under 42 CFR §414.1380. Reporting is voluntary for many small practices, so absence of a MIPS score is not a quality signal.

Board certification through an ABMS or AOA member board signals voluntary post-licensure examination plus continuous Maintenance of Certification cycles. Verify any individual provider's status through certificationmatters.org (ABMS) or osteopathic.org (AOA).

THERESA BRENNAN, MD appears in the CMS NPPES registry as a Internal Medicine Physician provider holding MD credentials at 200 HAWKINS DR, IOWA CITY, IA, 52242, with a listed phone of (319) 356-1607. NPI 1063400620 was issued on 10/07/2005. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what BRENNAN most recently submitted to CMS rather than a vetted directory listing, which is why patients should always confirm the practice is still at this location before scheduling.

Medicare Part D records for calendar year 2023 show 959 prescription claims written by this provider, covering 109 Medicare beneficiaries and totaling roughly $88K in drug spend, split 9% brand-name and 91% generic by claim count. These figures capture only Medicare Part D — commercial insurance, Medicaid, and cash-pay prescriptions are not included, and any drug-beneficiary cell under 11 is suppressed by CMS for patient privacy.

Internal Medicine Physician is a high-volume specialty nationwide, with 172,858 enrolled providers across 56 states and an average of 2,716 Part D claims per prescriber, so the context for interpreting these metrics differs meaningfully from a primary-care baseline. Important: PlainDoctor is a directory of publicly available government data, not medical advice, a malpractice database, or a quality rating. Inclusion here does not imply a recommendation, and absence of complaints or sanctions on this page does not mean none exist — always verify credentials through the NPPES NPI Registry, your state medical board, and the ABMS or AOA before making healthcare decisions.

Practice Address

200 HAWKINS DR
IOWA CITY, IA 52242

Provider Details

NPI 1063400620
Specialty Internal Medicine Physician
Credentials MD
Gender Female
NPI Issued 10/07/2005

Hospital and facility affiliations

Facilities where THERESA BRENNAN, MD bills Medicare from. Star ratings (1-5) are CMS Hospital Compare's "Hospital overall rating" — a composite of mortality, readmission, patient experience, safety, timely care, and efficient use of medical imaging measures. Source: CMS Care Compare.

STATE UNIVERSITY OF IOWA
IOWA CITY, IA

Affiliations sourced from CMS Doctors and Clinicians National Downloadable File; hospital ratings from CMS Hospital General Information dataset (cross-referenced by facility name + state).

Brand vs generic prescribing mix · Generic-heavy

THERESA BRENNAN, MD — brand share 9.0%
Specialty average (est.)

9% brand-name claims vs 91% generic, on 959 2023 Medicare Part D claims.

The federal Medicare Part D Generic Dispensing Rate national benchmark sits near 90% generic / 10% brand for primary-care prescribers, per CMS Office of the Actuary 2024 estimates. Higher brand share is common in specialty prescribing where generic equivalents are not available.

Medicare Part D Prescribing Data

CMS Medicare Part D prescriber-level data for calendar year 2023.

959
Total Claims
$88K
Total Drug Cost
109
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
2,441
Total Day Supply
72,813
Brand vs Generic
9% brand / 91% generic
Brand Drug Cost
$68K
Generic Drug Cost
$20K

Patient Demographics

Average Patient Age
72.7 years
Avg HCC Risk Score
1.68
Gender Split
41% female / 59% male

Top Prescribed Drugs (Medicare Part D)

Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.

What THERESA BRENNAN, MD prescribes most

Top Medicare Part D drugs by claim count, 2023

claims
Source CMS Medicare Part D Prescriber Public Use File As of 2023
Drug Claims
Atorvastatin Calcium
98
Losartan Potassium
91
Metoprolol Succinate
87
Furosemide
72
Lisinopril
56
Rosuvastatin Calcium
54
Amlodipine Besylate
45
Eliquis
Apixaban
43
Carvedilol
40
Potassium Chloride
35

* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.

Internal Medicine Physician Overview

How THERESA BRENNAN, MD fits within the Internal Medicine Physician landscape nationally.

172,858
Internal Medicine Physician Providers in US
56
States with Internal Medicine Physician
2,716
Avg Claims per Provider

THERESA BRENNAN, MD's 959 claims are below the specialty average of 2,716.

Nearby Internal Medicine Physician Providers in Iowa

Other clinicians with the same primary specialty enrolled in Iowa, drawn from the same CMS NPPES roster as BRENNAN.

Compare Internal Medicine Physician nationally: see state-by-state distribution →

Frequently Asked Questions

What is THERESA BRENNAN, MD's specialty?
THERESA BRENNAN, MD specializes in Internal Medicine Physician and practices in IOWA CITY, Iowa. Credentials: MD.
How much does THERESA BRENNAN, MD prescribe under Medicare Part D?
In 2023, THERESA BRENNAN, MD wrote 959 Medicare Part D claims totaling $88K in drug costs for 109 beneficiaries.
Where is THERESA BRENNAN, MD located?
THERESA BRENNAN, MD is located at 200 HAWKINS DR, IOWA CITY, IA, 52242. Phone: (319) 356-1607.
What is THERESA BRENNAN, MD's NPI number?
THERESA BRENNAN, MD's National Provider Identifier (NPI) is 1063400620, issued on 10/07/2005.
Does THERESA BRENNAN, MD prescribe more brand-name or generic drugs?
THERESA BRENNAN, MD's prescribing is 9% brand-name and 91% generic drugs by claim count, with $68K in brand drug costs.
How many Internal Medicine Physician providers are there in the US?
There are 172,858 Internal Medicine Physician providers across 56 states in the US. The average Internal Medicine Physician provider writes 2,716 Medicare Part D claims per year.
What drugs does THERESA BRENNAN, MD prescribe most often?
Based on 2023 Medicare Part D data, THERESA BRENNAN, MD's most frequently prescribed drugs include Atorvastatin Calcium, Losartan Potassium, Metoprolol Succinate. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does THERESA BRENNAN, MD accept Medicare?
THERESA BRENNAN, MD appears in CMS Medicare data with 959 Part D claims and 109 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify THERESA BRENNAN, MD's credentials?
THERESA BRENNAN, MD's NPI is 1063400620 with credentials MD. You can verify this through the NPPES NPI Registry, check state medical board records, and confirm board certification through the ABMS or AOA.

Data Sources

Provider Directory
CMS National Plan and Provider Enumeration System (NPPES), download.cms.gov/nppes, updated monthly. Contains NPI, specialty, credentials, and practice location.
Specialty Classification
NUCC Health Care Provider Taxonomy (nucc.org), the industry standard for classifying provider specialties in Medicare and Medicaid billing.
Prescribing Data
CMS Medicare Part D Prescriber Public Use File (2023). Includes claims, drug costs, beneficiaries, and opioid prescribing rates.
Limitations
Provider data is self-reported to CMS. Prescribing data reflects Medicare Part D only and does not include commercial insurance, Medicaid, or cash prescriptions. Claims below 11 beneficiaries are suppressed by CMS for privacy.

See our complete data methodology for details on how we collect and process government data.

Data as of April 2026 (NPPES) / 2023 (Medicare Part D). Source: Centers for Medicare & Medicaid Services (CMS).

Disclaimer: Data from CMS NPPES and Medicare Part D. PlainDoctor does not rate or rank providers. Provider information is self-reported and may not be current. Always verify information directly with the provider. About · Methodology