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

Dr. Alexander John Greenstein, MD

Individual provider Surgery Physician · NPI 1992964035

Dr. Alexander John Greenstein, MD practises General Surgery in New York, New York. Graduated from Js Weill Medical College, Cornell University in 2003, 23 years ago. Practices with Icahn School of Medicine at Mount Sinai, a 2,791-clinician group, accepts Medicare assignment and offers telehealth. Licensed in New York.

Years since qualifying
23
Trained at
Js Weill Medical College, Cornell University
Licensed in
NY
In the registry since
2008
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

5 E 98th St 15th Fl Box 1259
New York, NY 10029-6501 Not confirmed with CMS for 11 years — call before visiting
Phone: (212) 241-8679
Fax: (212) 534-2654
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Surgery Physician (primary) Taxonomy 208600000X · Licence 60 233708 (NY)

Record details

NPI number1992964035
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedJune 4, 2008
Last updated in NPPESOctober 8, 2014

Medicare enrollment

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

Medicare specialtyGENERAL SURGERY
Medical schoolJS WEILL MEDICAL COLLEGE, CORNELL UNIVERSITY
Graduated 2003 (23 years in practice)
Group practice Icahn School Of Medicine At Mount Sinai — 2791 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
TelehealthOffers telehealth services
Practice locations2 on file with Medicare

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Colonoscopy 1–10 times
Removal of tissue 1–10 times

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

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 patients115
Services billed 242 a service is one billed item, such as a visit, a test or a procedure
Average patient age71

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.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician. Those with a page here are linked.

  • Mount Sinai Hospital Hospital · New York, NY
  • Vns Of Ny Home Care Chha Home health agency · New York, NY

Colleagues at Icahn School of Medicine at Mount Sinai

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 2791 clinicians in the practice; 12 are shown here.

Other providers in New York