Mara Horwitz, MD
NPI 1649613332 · Rheumatology Physician · Saint Louis, MO
Enrolled with Medicare as Practitioner - Rheumatology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mara Horwitz, MD is a Rheumatology Physician provider in Saint Louis, MO (NPI 1649613332).
Provider details
- NPI number
- 1649613332
- Entity type
- Individual
- Primary specialty
- Rheumatology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Female
- Sole proprietor
- No
- License
- 2016009340 (MO)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Allopathic & Osteopathic Physicians
Student, Health Care
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure33% of score
13 yrs in NPPES registry
- Profile completeness33% of score
100% of core fields populated
- Practice footprint20% of score
1 documented practice location
- Open Payments transparency13% of score
Has Open Payments disclosures (2024)
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 prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 4 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Prednisone | 65 | 16 |
| Methotrexate Sodiumbrand: Methotrexate | 45 | 11 |
| Leucovorin Calcium | 15 | — |
| Tocilizumabbrand: Actemra | 12 | — |
Medicare Part D only. These counts cover prescriptions paid through Medicare Part D in 2024 — they do notinclude cash-pay, commercial-insurance, Medicaid, or Part B–administered drugs, and badly undercount high cash-pay categories (e.g. GLP-1 weight-loss, testosterone, and ED medications). Any drug with 10 or fewer claims is omitted by CMS, and beneficiary counts under 11 are suppressed — so a missing drug means no Part D record, never zero. This is a factual claims summary, not an endorsement, not medical advice, and not a consumer report. Source: CMS Medicare Part D Prescribers — by Provider and Drug.
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$83 across 4 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2013-04-11
- Last updated
- 2021-02-05
- Certified
- 2021-02-05
Frequently asked questions
- What is Mara Horwitz's NPI number?
- Mara Horwitz's National Provider Identifier (NPI) is 1649613332, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mara Horwitz's specialty?
- Mara Horwitz is listed in the NPPES registry with a primary specialty of Rheumatology Physician (Allopathic & Osteopathic Physicians).
- Where is Mara Horwitz located?
- Mara Horwitz's practice location on file with NPPES is 1225 S Grand Blvd, Saint Louis, MO 63104-1016.
- What is Mara Horwitz's phone number?
- The practice phone number listed in the NPPES registry for Mara Horwitz is (314) 977-8833.
- Does Mara Horwitz accept Medicare?
- Mara Horwitz is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mara Horwitz's NPI active?
- Yes — Mara Horwitz's NPI (1649613332) is active in the NPPES registry as of the last update on 2021-02-05.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.