Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of August 10, 2026.
NPIDirectory

Mark A Isaeff, MD

Individual provider Internal Medicine Physician · NPI 1104815075

Mark A Isaeff, MD practises Internal Medicine in San Antonio, Texas. Graduated from Georgetown University School of Medicine in 1998, 28 years ago. Practices as a sole proprietor and accepts Medicare assignment. Licensed in Texas.

Years since qualifying
28
Trained at
Georgetown University School of Medicine
Licensed in
TX
In the registry since
2005
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

1303 McCullough Ave Ste 542
San Antonio, TX 78212-5607 Not confirmed with CMS for 15 years — call before visiting
Phone: (210) 572-4431
Fax: (210) 572-4435
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Internal Medicine Physician (primary) Taxonomy 207R00000X · Licence K8638 (TX)

Record details

NPI number1104815075
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorYes
NPI enumeratedOctober 13, 2005
Last updated in NPPESApril 21, 2011

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyINTERNAL MEDICINE
Medical schoolGEORGETOWN UNIVERSITY SCHOOL OF MEDICINE
Graduated 1998 (28 years in practice)
Accepts Medicare assignment Yes — accepts the Medicare-approved amount

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients158
Services billed 419 a service is one billed item, such as a visit, a test or a procedure
Average patient age78

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Food and Beverage $125 1 payment · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

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