MARK A. ISAEFF, MD PA
NPI 1891090221
Internal Medicine in San Antonio, TX
About Mark A. Isaeff, Md Pa NPPES
Official registry information on file with the National Plan and Provider Enumeration System.
MARK A. ISAEFF, MD PA (NPI 1891090221) is a healthcare organization registered as an internal medicine in San Antonio, Texas and active in the NPI registry since January 2011. The organization lists Mark A Isaeff, President, as its authorized official.
NPPES Registry Identity
Specialties & Licenses
Other Identifiers 2
Group Practice 1
Medicare Participation & PECOS CMS
Medicare enrollment and the clinicians who bill Medicare through this organization, from CMS.
Medicare Enrollment Status
Enrolled in Medicare (PECOS)
Mark A. Isaeff, Md Pa is registered in the CMS Provider Enrollment, Chain and Ownership System (PECOS).
Clinicians Billing Medicare Through This Organization
Medicare enrollment records show 1 clinician reassigns Medicare billing to Mark A. Isaeff, MD PA, which bills Medicare for the services this clinician delivers.
Clinician (1)
San Antonio, TX 78212
Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.
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 Mark A. Isaeff, MD PA's NPI number?
The NPI number for Mark A. Isaeff, MD PA is 1891090221. It was assigned to this organization in the NPPES registry on January 16, 2011.
Where is Mark A. Isaeff, MD PA located?
Mark A. Isaeff, MD PA is located at 1303 Mccullough Ave 542, San Antonio, TX 78212. The listed phone number is (210) 572-4431.
What is Mark A. Isaeff, MD PA's specialty?
The primary specialty registered for this NPI is Internal Medicine with taxonomy code 207R00000X.
Is Mark A. Isaeff, MD PA enrolled in Medicare?
Yes. Mark A. Isaeff, MD PA is registered in the Medicare PECOS enrollment system.
How many clinicians bill Medicare through Mark A. Isaeff, MD PA?
According to the CMS Revalidation Reassignment List (October 2026 release), 1 clinician (Internal Medicine) reassigns their Medicare billing to Mark A. Isaeff, MD PA. A 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 the clinician's services. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.
When was this NPI record last updated?
The NPPES record for Mark A. Isaeff, MD PA was last updated on April 14, 2011. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 15 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.
# Mark A. Isaeff, Md Pa · NPI 1891090221
Internal Medicine organization in San Antonio, Texas. Organization record, active in the CMS NPPES registry since January 16, 2011.
## Identity
- **NPI:** 1891090221 (Entity type: Organization)
- **Enumerated:** January 16, 2011
- **Primary specialty:** Internal Medicine · taxonomy 207R00000X
- **Organization subpart:** No
- **Authorized official:** Mark Isaeff, PRESIDENT
## Practice location
- **Address:** 1303 MCCULLOUGH AVE, 542, San Antonio, TX 78212-5609
- **Phone:** (210) 572-4431 · **Fax:** (210) 572-4435
## Medicare
- **Medicare:** Enrolled in Medicare (PECOS)
- **Clinicians billing through this organization:** 1 clinician (Internal Medicine) reassigns Medicare billing to this organization (form CMS-855R) · CMS Revalidation Reassignment List, October 2026 release
## Record status
- **NPPES last updated:** April 14, 2011
- **Other identifiers:** Medicaid 218930001 (TX); Medicare PIN TXB118188 (TX)
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Source: [NPI Profile](https://npiprofile.com/npi/1891090221) · Data from the CMS NPPES public registry.