Mara Harmelin Horwitz, MD
Rheumatology Physician · Saint Louis, MO
Mara Harmelin Horwitz, MD is a rheumatology physician with a practice address in Saint Louis, Missouri, and NPI 1649613332, issued on Apr 11, 2013. Check the license (Missouri 2016009340, as entered in NPPES) on the Missouri Board of Registration for the Healing Arts; the Medicare figures below come from public CMS files.
- Name
- Mara Harmelin Horwitz
- Credential
- MD
- Primary taxonomy
- Rheumatology Physician 207RR0500X
- License number
- 2016009340 MO
Self-reported in NPPES; status is on the state search - Practice location
- 1225 S Grand Blvd, Saint Louis, MO 63104
- Phone
- (314) 977-8833
- Enumerated
- Apr 11, 2013
- Record last updated
- Feb 5, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20221028002506); accepts Medicare assignment
- Medical or professional school
- Southern Illinois University School Of Medicine, 2013
- Entity
- Type 1 · individual
8 nearest rheumatology physician records → All 151 in Missouri → Look up another NPI →
Also registered at 1225 S Grand Blvd
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Mara Harmelin Horwitz in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMissouri Board of Registration for the Healing Arts
Search for license 2016009340Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
88% fewer Medicare Part D claims than the average rheumatology physician in 2024
235 Medicare Part D claims for 34 beneficiaries, against an average of 1,978 among the 6,301 providers of this specialty who prescribed in Part D.
Most prescribed
- Prednisone65 claims
- Methotrexate45 claims
- Leucovorin Calcium15 claims
- Actemra12 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Industry payments in 2024: $82.71
4 payments; by number, the most common kind was food and beverage; the largest payer was Amgen Inc. The 4,486 providers of this specialty with any payment received $8,538.33 on average. Payments are reported by manufacturers, not by the provider, and are not a sign of wrongdoing.
Source: CMS Open Payments, program year 2024 (openpaymentsdata.cms.gov); average among providers of this specialty with at least one payment.
Bills Medicare through one group practice
- Multicare Health SystemAuburn, WA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Mara Harmelin Horwitz among 151 rheumatology physician records in Missouri
Mara Harmelin Horwitz, MD is one of 151 rheumatology physician records with a practice address in Missouri. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2013, is newer than 70% of them.
- NPI issued2013 · 70% of these records are older, 25% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 69% of these records are
- Graduated2013 · median 2005 among the 103 with a school on file
- Record last updated2021 · 48% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RR0500X and a Missouri practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Rheumatology Physician providers in Missouri
There are 151 rheumatology physician records in Missouri.
All 151 in Missouri → Every provider in Saint Louis → Rheumatology Physician nationwide →
The 8 rheumatology physician records with the nearest ZIP codes
- Rama Atluri, M.D.Saint Louis, MO 631041063507531
- Adam Kilian, M.D.Saint Louis, MO 631041497174015
- Sonal Mehra, MBBSSaint Louis, MO 631041265383863
- Terry Moore, M.D.St Louis, MO 631041114014867
- Muhammad Zaheer, MDSaint Louis, MO 631041356725832
- Aisha ZiaSaint Louis, MO 631041366071433
- Colin Diffie, MDSaint Louis, MO 631061942616404
- Amy Joseph, MDSaint Louis, MO 631061699730853
Common questions
What is Mara Harmelin Horwitz, MD's NPI number?
Mara Harmelin Horwitz, MD's National Provider Identifier (NPI) is 1649613332, issued on Apr 11, 2013. An NPI identifies a provider in billing; it is not a license.
Where is Mara Harmelin Horwitz, MD located?
The NPPES record lists a practice address at 1225 S Grand Blvd, Saint Louis, MO, 63104. Phone: (314) 977-8833. Providers update this record themselves, so call before visiting.
How can I verify Mara Harmelin Horwitz, MD's license?
NPPES lists Missouri license number 2016009340, as entered by the provider. Search the Missouri Board of Registration for the Healing Arts at https://www.fsmb.org/contact-a-state-medical-board/. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Mara Harmelin Horwitz, MD prescribe under Medicare Part D?
In 2024, Mara Harmelin Horwitz, MD had 235 Medicare Part D claims for 34 beneficiaries; the average among rheumatology physician prescribers was 1,978. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.