Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

John Mark Flack, MD, MPH

Individual provider Internal Medicine Physician · NPI 1164450987

John Mark Flack, MD, MPH practises Internal Medicine in Springfield, Illinois. Qualified in 1982, 44 years ago. Practices with SIU Physicians and Surgeons Inc, a 316-clinician group and accepts Medicare assignment. Licensed in Illinois.

Years since qualifying
44
Licensed in
IL
In the registry since
2006
Specialties on file
2
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.
MPH — Master of Public Health
A graduate degree in population health.

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Practice location Address checks out

751 N Rutledge St Ste 1100
Springfield, IL 62702-4968
Phone: (217) 545-8000
Fax: (217) 545-4735
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Hypertension Specialist Physician (primary) Taxonomy 207RH0005X · Licence 036-138254 (IL)
Internal Medicine Physician Taxonomy 207R00000X · Licence 036-138254 (IL)

Record details

NPI number1164450987
Entity typeIndividual (Type 1)
GenderMale
Credentials MD , MPH
Sole proprietorNo
NPI enumeratedJune 29, 2006
Last updated in NPPESOctober 21, 2020
Certification dateOctober 21, 2020

Medicare enrollment

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

Medicare specialtyINTERNAL MEDICINE
Medical schoolOTHER
Graduated 1982 (44 years in practice)
Group practice Siu Physicians And Surgeons Inc — 316 clinicians
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 patients44
Services billed 55 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.

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.

Consulting Fee $22,655 12 payments
Travel and Lodging $2,155 10 payments · travel or lodging paid or reimbursed, such as to attend a conference
Food and Beverage $826 11 payments · 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.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at SIU Physicians and Surgeons Inc

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 316 clinicians in the practice; 12 are shown here.

Other providers in Springfield