DR. THOMAS MICHAEL DEFER MD
NPI 1023036464
Internal Medicine in Saint Louis, MO
About Dr. Thomas Michael Defer Md NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
DR. THOMAS MICHAEL DEFER MD (NPI 1023036464) is an individual internal medicine provider in Saint Louis, Missouri, licensed in Missouri (R4N34) and active in the NPI registry since July 2006. He is enrolled in Medicare PECOS, is affiliated with Barnes Jewish Hospital, and is a graduate of University Of Missouri, Columbia School Of Medicine (1989).
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 1
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. Thomas Michael Defer 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 Thomas Defer reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.
Saint Louis, MO 63110
- Reassigned Medicare billing, Missouri enrollment
- 1,133 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.
Areas of Expertise CMS Part B claims 2
Services this provider delivered to Medicare fee-for-service patients, from the CMS Medicare utilization data. Higher counts generally reflect more experience with a service; care delivered outside Medicare is not included.
Hospital Affiliations CMS Care Compare
Hospitals where this provider delivers care, identified from recent Medicare claims and place-of-service records.
Barnes Jewish Hospital
Acute Care Hospitals · Saint Louis, MOPhysician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 63110 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.
Medicare Quality Performance CMS QPP · MIPS
Performance in the CMS Quality Payment Program: the MIPS final score across four weighted categories, and the individual quality measures reported to Medicare.
Other Providers at the Same Location NPPES 12
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
SAINT LOUIS, MO 63110
SAINT LOUIS, MO 63110
SAINT LOUIS, MO 63110
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 Thomas Defer's NPI number?
The NPI number for Thomas Defer is 1023036464. It was assigned to this individual provider in the NPPES registry on July 17, 2006.
Where is Thomas Defer located?
Thomas Defer practices at 4950 Childrens Pl Dept Internal Med, Saint Louis, MO 63110. The listed phone number is (314) 362-5060.
What is Thomas Defer's specialty?
The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.
Is Thomas Defer enrolled in Medicare?
Yes. Thomas Defer 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 Thomas Defer's services?
According to the CMS Revalidation Reassignment List (October 2026 release), Thomas Defer reassigns Medicare benefits to Washington University (Saint Louis, MO). 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 Thomas Defer's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
What insurance does Thomas Defer accept?
Health plans from Cox HealthPlans and UnitedHealthcare list Thomas Defer 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 Thomas Defer affiliated with any hospitals?
According to CMS data, Thomas Defer is affiliated with Barnes Jewish Hospital.
When was this NPI record last updated?
The NPPES record for Thomas Defer was last updated on April 17, 2025. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 18 months 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. Thomas Michael Defer, MD · NPI 1023036464
Internal Medicine physician in Saint Louis, Missouri. Individual provider, active in the CMS NPPES registry since July 17, 2006.
## Identity
- **NPI:** 1023036464 (Entity type: Individual)
- **Enumerated:** July 17, 2006
- **Primary specialty:** Internal Medicine · taxonomy 207R00000X
- **State license:** R4N34 (Missouri)
- **Sole proprietor:** No
## Practice location
- **Address:** 4950 CHILDRENS PL, DEPT INTERNAL MED, Saint Louis, MO 63110-1000
- **Phone:** (314) 362-5060 · **Fax:** (314) 362-6959
## 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:** Washington University (NPI 1992746903, Saint Louis, MO), under Medicare reassignment (form CMS-855R) · CMS Revalidation Reassignment List, October 2026 release
- **Medical school:** University Of Missouri, Columbia School Of Medicine, class of 1989
## Record status
- **NPPES last updated:** April 17, 2025
- **Other identifiers:** Medicaid 203721238 (MO)
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Source: [NPI Profile](https://npiprofile.com/npi/1023036464) · Data from the CMS NPPES public registry.