DR. GILLIAN ALISON SOUTHWELL M.D.
NPI 1396899399
Internal Medicine in Washington, DC
About Dr. Gillian Alison Southwell M.d. NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
DR. GILLIAN ALISON SOUTHWELL M.D. (NPI 1396899399) is an individual internal medicine provider in Washington, District Of Columbia, licensed in District Of Columbia (MD31790) and active in the NPI registry since January 2007. She is enrolled in Medicare PECOS.
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 2
Medicare Participation & PECOS CMS
Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.
Medicare Enrollment Status
Enrolled in Medicare (PECOS)
Dr. Gillian Alison Southwell M.d. is registered in the CMS Provider Enrollment, Chain and Ownership System (PECOS).
Medicare Billing Reassignments
3Medicare enrollment records show Gillian Southwell reassigns Medicare billing to 3 organizations. Each organization bills Medicare for the services this provider delivers there; the nearest is listed first.
Washington, DC 20010
- Reassigned Medicare billing, District of Columbia enrollment
- 3,530 clinicians in this Medicare group
Washington, DC 20010
- Reassigned Medicare billing, District of Columbia enrollment
- Medicare enrollment name: Whc Physician Group LLC
- 613 clinicians in this Medicare group
Washington, DC 20010
- Reassigned Medicare billing, District of Columbia enrollment
- 87 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
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.
Physician Visit Costs CMS claims · ZIP area
Typical Medicare office-visit costs in the 20010 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 6
Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.
WASHINGTON, DC 20010
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 Gillian Southwell's NPI number?
The NPI number for Gillian Southwell is 1396899399. It was assigned to this individual provider in the NPPES registry on January 23, 2007.
Where is Gillian Southwell located?
Gillian Southwell practices at 110 Irving Street Suite 4b1, Washington, DC 20010. The listed phone number is (202) 877-5975.
What is Gillian Southwell's specialty?
The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.
Is Gillian Southwell enrolled in Medicare?
Yes. Gillian Southwell is registered in the Medicare PECOS enrollment system.
Which organizations bill Medicare for Gillian Southwell's services?
According to the CMS Revalidation Reassignment List (October 2026 release), Gillian Southwell reassigns Medicare benefits to 3 organizations: Medstar Medical Group II LLC (Washington, DC), Whc Emerg Phys (Washington, DC) and Medstar Total Elder Care LLC (Washington, DC). Each 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 Gillian Southwell's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.
When was this NPI record last updated?
The NPPES record for Gillian Southwell was last updated on July 8, 2007. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 19 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. Gillian Alison Southwell, M.D. · NPI 1396899399
Internal Medicine physician in Washington, District of Columbia. Individual provider, active in the CMS NPPES registry since January 23, 2007.
## Identity
- **NPI:** 1396899399 (Entity type: Individual)
- **Enumerated:** January 23, 2007
- **Primary specialty:** Internal Medicine · taxonomy 207R00000X
- **State license:** MD31790 (District of Columbia)
- **Sole proprietor:** No
## Practice location
- **Address:** 110 IRVING STREET, SUITE 4B1, Washington, DC 20010
- **Phone:** (202) 877-5975 · **Fax:** (202) 877-2718
## Medicare
- **Medicare:** Enrolled in Medicare (PECOS)
- **Ordering & referring:** eligible for Part B labs & imaging, durable medical equipment, home health, power mobility devices
- **Bills Medicare through:** 3 organizations under Medicare reassignment (form CMS-855R): Medstar Medical Group II LLC (NPI 1023836137, Washington, DC); Whc Emerg Phys (NPI 1306260625, Washington, DC); Medstar Total Elder Care LLC (NPI 1750752911, Washington, DC) · CMS Revalidation Reassignment List, October 2026 release
## Record status
- **NPPES last updated:** July 8, 2007
- **Other identifiers:** Medicare UPIN H94450; Medicare ID-Type Unspecified K679G947
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Source: [NPI Profile](https://npiprofile.com/npi/1396899399) · Data from the CMS NPPES public registry.