2026 NPPES data Internal Medicine Physician NPI 1821264425 M.D., M.S.
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Thomas Withuhn, M.D., M.S.

Internal Medicine Physician in Owings Mills, Maryland. This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 172,858 in Internal Medicine Physician, and covers specialty classification, practice address, and Medicare Part D prescribing data when reported. According to CMS, every field reflects the provider's official federal registration, see our methodology.

Federal data, no proprietary rating. We show these CMS records as-is - no composite score, no star rating, no editorial opinion layered on top.
Prescribing volume
5K
Medicare Part D claims · 376 beneficiaries · Internal Medicine Physician avg: 3K
Generic prescribing
89%
generic claims · 9% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$2.4K
131 payments · CMS Open Payments (Sunshine Act)
Compiled from official public sources by the PlainDoctor editorial team.

What the federal data shows

Thomas Withuhn, M.D., M.S. filed 4,519 Medicare Part D claims in 2023 as a Internal Medicine Physician in Owings Mills, Maryland, prescribing 89% generic.

5K
Part D claims, 2023
89%
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.

Thomas Withuhn, M.D., M.S.'s Medicare Part D volume vs every U.S. prescriber

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

4,519 Top 7% higher than 93% 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%). Below this entry. 1,000–1,200: 31,827 prescribers (2%). Below this entry. 1,200–1,400: 26,224 prescribers (2%). Below this entry. 1,400–1,600: 21,710 prescribers (2%). Below this entry. 1,600–1,800: 19,072 prescribers (1%). Below this entry. 1,800–2,000: 16,451 prescribers (1%). Below this entry. 2K+: 213,991 prescribers (16%). This entry sits in this band. 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)

Thomas Withuhn, M.D., M.S. practices in an ABMS-board-eligible specialty and shows active CMS Medicare participation + 2 hospital affiliations - 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 Thomas Withuhn, M.D., M.S.?

Quality data not reported

NPI registry status

Active

Issued 05/02/2008

NPI 1821264425

Primary specialty

Internal Medicine Physician

High-volume

172,858 US NPIs in this specialty

Medicare Part D claims

4,519 66% vs specialty avg

2023 prescription claims

Specialty avg: 2,716

Specialty distribution in Maryland

How Internal Medicine Physician compares to other specialties among Maryland providers

Maryland providers

Largest specialties in Maryland (% of in-state providers)

Behavior Technician - 14.1%Behavior Technician14.1%Clinical Social Worker - 5.5%Clinical Social Worker5.5%Student in an Organized Health Care Education/Training Program - 4.5%Student in an Organized Health Care Education/Training Program4.5%Home Health Aide - 4.4%Home Health Aide4.4%Physical Therapist - 3.9%Physical Therapist3.9%Pharmacist - 3.6%Pharmacist3.6%Internal Medicine Physician - 2.8%Internal Medicine Physician2.8%
Largest specialties in Maryland (% of in-state providers)

Board certification

Not published by CMS

CMS does not publish a per-provider board-certification field in NPPES. PlainDoctor does not have a reliable per-specialty certification rate to show for Internal Medicine Physician. Verify directly:

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).

Thomas Withuhn, M.D., M.S. appears in the CMS NPPES registry as a Internal Medicine Physician provider holding M.D., M.S. credentials at 10084 REISTERSTOWN RD STE 200A, Owings Mills, MD, 21117, with a listed phone of (410) 552-5050. NPI 1821264425 was issued on 05/02/2008. Because NPPES data is self-reported by the provider and refreshed monthly, the address, phone, and specialty reflect what Withuhn 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 4,519 prescription claims written by this provider, covering 376 Medicare beneficiaries and totaling roughly $490K in drug spend, split 9% brand-name and 89% generic by claim count, with an opioid prescribing rate of 3.9%. 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

10084 REISTERSTOWN RD STE 200A
Owings Mills, MD 21117

Provider Details

NPI 1821264425
Specialty Internal Medicine Physician
Credentials M.D., M.S.
Gender Male
NPI Issued 05/02/2008

Hospital and facility affiliations

Facilities where Thomas Withuhn, M.D., M.S. 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.

Agape Physical Therapy And Sports Rehabilitation LP
Forest Hill, MD
Lifebridge Community Physicians Inc
Westminster, MD

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

Industry payments received (2024) - CMS Open Payments transparency data

The federal Physician Payments Sunshine Act (part of the Affordable Care Act) requires drug and medical-device manufacturers + group purchasing organizations to publicly report payments and other transfers of value to physicians and teaching hospitals. The data below covers 2024 for Thomas Withuhn, M.D., M.S.. Source: openpaymentsdata.cms.gov.

Total received

$2.4K

Largest payer

Novo Nordisk Inc

Most common payment type

Food and Beverage

Industry payments are not necessarily indicators of bias, they include research funding, consulting fees for evidence-based work, royalties for inventions, food at conferences, and similar items. The disclosure exists for transparency. Read our methodology for how we interpret this data.

Brand vs generic prescribing mix · Generic-heavy

Thomas Withuhn, M.D., M.S. - brand share 9.0%
Internal Medicine Physician average

9% brand-name claims vs 89% generic, on 4,519 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.

4,519
Total Claims
$490K
Total Drug Cost
376
Medicare Beneficiaries

Prescribing Breakdown

30-Day Fills
10,017
Total Day Supply
288,622
Brand vs Generic
9% brand / 89% generic
Brand Drug Cost
$380K
Generic Drug Cost
$107K
Opioid Claims
175 (3.9% rate)
Antibiotic Claims
147

Patient Demographics

Average Patient Age
73.1 years
Avg HCC Risk Score
1.05
Gender Split
52% female / 48% male
Age Distribution
<65: 34, 65-74: 174, 75-84: 132, 85+: 36

Top Prescribed Drugs (Medicare Part D)

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

What Thomas Withuhn, M.D., M.S. 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
173
Amlodipine Besylate
168
Rosuvastatin Calcium
161
Levothyroxine Sodium
129
Lisinopril
128
Losartan Potassium
104
Omeprazole
98
Metformin Hcl
89
Lorazepam
82
Furosemide
81

* 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 Thomas Withuhn, M.D., M.S. 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

Thomas Withuhn, M.D., M.S.'s 4,519 claims are above the specialty average of 2,716.

Nearby Internal Medicine Physician Providers in Maryland

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

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

Before you book an appointment

Use this federal record as your verification checklist, not as a recommendation.

  • Confirm the NPI record is current in the official CMS registry, providers update their own NPPES details, and moves can lag. Verify this NPI
  • Check the active license and any disciplinary history with the Maryland medical board, federal registration is not a license check. Credential verification guide
  • Weigh a second option: compare this provider with a nearby Internal Medicine Physician peer on Medicare volume and prescribing patterns. Compare providers

Medicare Part D and MIPS figures describe practice patterns in federal programs only, they are not quality ratings, and PlainDoctor does not rate, rank, or recommend providers.

Frequently Asked Questions

What is Thomas Withuhn, M.D., M.S.'s specialty?
Thomas Withuhn, M.D., M.S. specializes in Internal Medicine Physician and practices in Owings Mills, Maryland. Credentials: M.D., M.S..
How much does Thomas Withuhn, M.D., M.S. prescribe under Medicare Part D?
In 2023, Thomas Withuhn, M.D., M.S. wrote 4,519 Medicare Part D claims totaling $490K in drug costs for 376 beneficiaries.
Where is Thomas Withuhn, M.D., M.S. located?
Thomas Withuhn, M.D., M.S. is located at 10084 REISTERSTOWN RD STE 200A, Owings Mills, MD, 21117. Phone: (410) 552-5050.
What is Thomas Withuhn, M.D., M.S.'s NPI number?
Thomas Withuhn, M.D., M.S.'s National Provider Identifier (NPI) is 1821264425, issued on 05/02/2008.
Does Thomas Withuhn, M.D., M.S. prescribe more brand-name or generic drugs?
Thomas Withuhn, M.D., M.S.'s prescribing is 9% brand-name and 89% generic drugs by claim count, with $380K in brand drug costs.
Does Thomas Withuhn, M.D., M.S. prescribe opioids?
Yes, Thomas Withuhn, M.D., M.S. had 175 opioid claims in 2023 with an opioid prescribing rate of 3.9%.
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 Thomas Withuhn, M.D., M.S. prescribe most often?
Based on 2023 Medicare Part D data, Thomas Withuhn, M.D., M.S.'s most frequently prescribed drugs include Atorvastatin Calcium, Amlodipine Besylate, Rosuvastatin Calcium. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Thomas Withuhn, M.D., M.S. accept Medicare?
Thomas Withuhn, M.D., M.S. appears in CMS Medicare data with 4,519 Part D claims and 376 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Thomas Withuhn, M.D., M.S.'s credentials?
Thomas Withuhn, M.D., M.S.'s NPI is 1821264425 with credentials M.D., M.S.. 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

Compiled from official public sources by the PlainDoctor editorial team.