NPI registry status
Active
2026 NPPES data Pediatric Rheumatology Physician NPI 1649613332 MD
Verify on CMS → Mara Horwitz, MD
Pediatric Rheumatology Physician in Saint Louis, Missouri.
This profile is drawn from the federal National Provider Identifier Registry (CMS NPPES), which lists more than 7 million U.S. healthcare providers - including 390 in Pediatric Rheumatology 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
185
Medicare Part D claims · 41 beneficiaries · Pediatric Rheumatology Physician avg: 200
Generic prescribing
90%
generic claims · 10% brand-name · higher generic rates reduce patient out-of-pocket costs
Industry payments
$82.71
4 payments · CMS Open Payments (Sunshine Act)
Source: CMS Medicare Part D Prescriber Public Use File, 2023
Compiled from official public sources by the PlainDoctor editorial team.
What the federal data shows
Mara Horwitz, MD filed 185 Medicare Part D claims in 2023 as a Pediatric Rheumatology Physician in Saint Louis, Missouri, prescribing 90% generic.
- 185
- Part D claims, 2023
- 90%
- 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.
Mara Horwitz, MD's Medicare Part D volume vs every U.S. prescriber
Total Medicare Part D claims, 2023, across all CMS prescribers nationally
185 35th percentile higher than 35% of 1,370,886 prescribers
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)
Mara Horwitz, 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 Mara Horwitz, MD?
Quality data not reportedPrimary specialty
Pediatric Rheumatology Physician
Medicare Part D claims
185 7% vs specialty avg
Specialty distribution in Missouri
How Pediatric Rheumatology Physician compares to other specialties among Missouri 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 Pediatric Rheumatology Physician. Verify directly:
How MIPS and board certification work
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).
Mara Horwitz, MD appears in the CMS NPPES registry as a Pediatric Rheumatology Physician provider holding MD credentials at 1225 S GRAND BLVD, Saint Louis, MO, 63104, with a listed phone of (314) 977-8833. NPI 1649613332 was issued on 04/11/2013.
Medicare Part D records for calendar year 2023 show 185 prescription claims written by this provider, covering 41 Medicare beneficiaries and totaling roughly $39K in drug spend, split 10% brand-name and 90% generic by claim count.
Pediatric Rheumatology Physician is a narrow specialty nationwide, with 390 enrolled providers across 43 states and an average of 200 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
Provider Details
| NPI | 1649613332 |
|---|---|
| Specialty | Pediatric Rheumatology Physician |
| Credentials | MD |
| Gender | Female |
| NPI Issued | 04/11/2013 |
Hospital and facility affiliations
Facilities where Mara Horwitz, 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.
Multicare Health System
Auburn, WA
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 Mara Horwitz, MD. Source: openpaymentsdata.cms.gov.
Total received
$83
Largest payer
Amgen 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 · Typical
Mara Horwitz, MD - brand share 10.0%
Pediatric Rheumatology Physician average
10% brand-name claims vs 90% generic, on 185 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.
185
Total Claims
$39K
Total Drug Cost
41
Medicare Beneficiaries
Prescribing Breakdown
- 30-Day Fills
- 283
- Total Day Supply
- 8,339
- Brand vs Generic
- 10% brand / 90% generic
- Brand Drug Cost
- $33K
- Generic Drug Cost
- $6K
Patient Demographics
- Average Patient Age
- 66.2 years
- Avg HCC Risk Score
- 1.78
- Age Distribution
- <65: 15, 65-74: 19, 75-84: N/A, 85+: N/A
Top Prescribed Drugs (Medicare Part D)
Top drugs by claim count for calendar year 2023. Based on Medicare Part D data only.
What Mara Horwitz, MD prescribes most
Top Medicare Part D drugs by claim count, 2023
- Prednisone
Prednisone
53 claims
- Methotrexate
Methotrexate
31 claims
- Hydroxychloroquine… 18
Hydroxychloroquine Sulfate
18 claims
- Allopurinol 13
Allopurinol
13 claims
| Drug | Claims |
|---|---|
| Prednisone | 53 |
| Methotrexate Methotrexate Sodium | 31 |
| Hydroxychloroquine Sulfate | 18 |
| Allopurinol | 13 |
* Counts below 11 are suppressed by CMS for patient privacy. Generic names shown where available from CMS Part D data.
Pediatric Rheumatology Physician Overview
How Mara Horwitz, MD fits within the Pediatric Rheumatology Physician landscape nationally.
390
Pediatric Rheumatology Physician Providers in US
43
States with Pediatric Rheumatology Physician
200
Avg Claims per Provider
Mara Horwitz, MD's 185 claims are below the specialty average of 200.
Nearby Pediatric Rheumatology Physician Providers in Missouri
Other clinicians with the same primary specialty enrolled in Missouri, drawn from the same CMS NPPES roster as Horwitz.
Dr. Mara Becker
M.D.
Kansas City, MO
Dr. Ashley Cooper
MD
Kansas City, MO
Dr. Austin Dalrymple
D.O.
Saint Louis, MO
Dr. Leslie Favier
M.D.
Kansas City, MO
Dr. Lampros Fotis
MD
Saint Louis, MO
Compare Pediatric Rheumatology 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 Missouri medical board, federal registration is not a license check. Credential verification guide
- Weigh a second option: compare this provider with a nearby Pediatric Rheumatology 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.
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Frequently Asked Questions
What is Mara Horwitz, MD's specialty? ▼
Mara Horwitz, MD specializes in Pediatric Rheumatology Physician and practices in Saint Louis, Missouri. Credentials: MD.
How much does Mara Horwitz, MD prescribe under Medicare Part D? ▼
In 2023, Mara Horwitz, MD wrote 185 Medicare Part D claims totaling $39K in drug costs for 41 beneficiaries.
Where is Mara Horwitz, MD located? ▼
Mara Horwitz, MD is located at 1225 S GRAND BLVD, Saint Louis, MO, 63104. Phone: (314) 977-8833.
What is Mara Horwitz, MD's NPI number? ▼
Mara Horwitz, MD's National Provider Identifier (NPI) is 1649613332, issued on 04/11/2013.
Does Mara Horwitz, MD prescribe more brand-name or generic drugs? ▼
Mara Horwitz, MD's prescribing is 10% brand-name and 90% generic drugs by claim count, with $33K in brand drug costs.
How many Pediatric Rheumatology Physician providers are there in the US? ▼
There are 390 Pediatric Rheumatology Physician providers across 43 states in the US. The average Pediatric Rheumatology Physician provider writes 200 Medicare Part D claims per year.
What drugs does Mara Horwitz, MD prescribe most often? ▼
Based on 2023 Medicare Part D data, Mara Horwitz, MD's most frequently prescribed drugs include Prednisone, Methotrexate, Hydroxychloroquine Sulfate. This reflects Medicare Part D prescriptions only and does not include commercial insurance or other payer types.
Does Mara Horwitz, MD accept Medicare? ▼
Mara Horwitz, MD appears in CMS Medicare data with 185 Part D claims and 41 Medicare beneficiaries in 2023. Contact the provider's office directly to confirm current Medicare enrollment and accepted plans.
How can I verify Mara Horwitz, MD's credentials? ▼
Mara Horwitz, MD's NPI is 1649613332 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
View source datasets and methodology notes
- 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.