DR. MARA HARMELIN HORWITZ MD
NPI 1649613332
Internal Medicine - Rheumatology in Saint Louis, MO
About Dr. Mara Harmelin Horwitz Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
DR. MARA HARMELIN HORWITZ MD (NPI 1649613332) is an individual rheumatology provider in Saint Louis, Missouri, licensed in Missouri (2016009340) and active in the NPI registry since April 2013. She is enrolled in Medicare PECOS, is affiliated with Tacoma General Allenmore Hospital, and is a graduate of Southern Illinois University School Of Medicine (2013).
NPPES Registry Identity
Specialties & Licenses 3
Accepted Insurance
Medicare Participation & PECOS CMS
Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.
Medicare Enrollment Status
Enrolled in Medicare and accepts Medicare assignment
Dr. Mara Harmelin Horwitz Md is registered in PECOS and agrees to accept the Medicare-approved amount as full payment. Medicare patients are not billed beyond the standard deductible and coinsurance.
Medicare Billing Reassignment
Medicare enrollment records show Mara Horwitz reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.
Spokane Valley, WA 99037
- Reassigned Medicare billing, Washington enrollment
- 4,383 clinicians in this Medicare group
Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.
Hospital Affiliations CMS Care Compare
Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.
Tacoma General Allenmore Hospital
Acute Care Hospitals · Tacoma, WAPhysician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 63104 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.
Other Providers at the Same Location NPPES 20
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
SAINT LOUIS, MO 63104
SAINT LOUIS, MO 63104
SAINT LOUIS, MO 63104
Frequently Asked Questions NPPES & CMS
Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.
What is Mara Horwitz's NPI number?
The NPI number for Mara Horwitz is 1649613332. It was assigned to this individual provider in the NPPES registry on April 11, 2013.
Where is Mara Horwitz located?
Mara Horwitz practices at 1225 S Grand Blvd, Saint Louis, MO 63104. The listed phone number is (314) 977-8833.
What is Mara Horwitz's specialty?
The primary specialty registered for this NPI is Internal Medicine, specializing in Rheumatology, with taxonomy code 207RR0500X.
Is Mara Horwitz enrolled in Medicare?
Yes. Mara Horwitz is registered in the Medicare PECOS system and accepts Medicare assignment, which means accepting the Medicare-approved amount as payment in full for covered services.
Which organization bills Medicare for Mara Horwitz's services?
According to the CMS Revalidation Reassignment List (October 2026 release), Mara Horwitz reassigns Medicare benefits to Multicare Health System (Spokane Valley, WA). The reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for Mara Horwitz's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
What insurance does Mara Horwitz accept?
Health plans from Ambetter Health, Premera Blue Cross Blue Shield of Alaska and Providence Health Plan list Mara Horwitz as in-network in at least one marketplace plan. Coverage varies by plan and year; verify with the insurer or the provider before a visit.
Is Mara Horwitz affiliated with any hospitals?
According to CMS data, Mara Horwitz is affiliated with Tacoma General Allenmore Hospital.
When was this NPI record last updated?
The NPPES record for Mara Horwitz was last updated on February 5, 2021. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 5 years ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.
# Dr. Mara Harmelin Horwitz, MD · NPI 1649613332
Rheumatology physician in Saint Louis, Missouri. Individual provider, active in the CMS NPPES registry since April 11, 2013.
## Identity
- **NPI:** 1649613332 (Entity type: Individual)
- **Enumerated:** April 11, 2013
- **Primary specialty:** Internal Medicine - Rheumatology · taxonomy 207RR0500X
- **State license:** 2016009340 (Missouri)
- **Sole proprietor:** No
## Practice location
- **Address:** 1225 S GRAND BLVD, Saint Louis, MO 63104-1016
- **Phone:** (314) 977-8833
## Medicare
- **Medicare:** Enrolled (PECOS); accepts Medicare assignment
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Bills Medicare through:** Multicare Health System (NPI 1336902345, Spokane Valley, WA), under Medicare reassignment (form CMS-855R) · CMS Revalidation Reassignment List, October 2026 release
- **Medical school:** Southern Illinois University School Of Medicine, class of 2013
## Record status
- **NPPES last updated:** February 5, 2021
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Source: [NPI Profile](https://npiprofile.com/npi/1649613332) · Data from the CMS NPPES public registry.