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

Dr. Mark Francis Grenquist, DO

Individual provider Internal Medicine Physician · NPI 1942300454

Dr. Mark Francis Grenquist, DO is a Hospitalist in Chelsea, Michigan. Graduated from Michigan State University College of Human Medicine in 2001, 25 years ago. Practices with Apogee Medical Group Michigan PC, a 44-clinician group and accepts Medicare assignment. Licensed in Michigan.

Years since qualifying
25
Trained at
Michigan State University College of Human Medicine
Licensed in
MI
In the registry since
2006
Specialties on file
2
What do these letters mean?
DO — Doctor of Osteopathic Medicine
A fully licensed physician, trained like an MD with additional musculoskeletal training. Equivalent practice rights in all 50 states.

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Practice location Address checks out

775 S Main St
Chelsea, MI 48118-1383 Not confirmed with CMS for 10 years — call before visiting
Phone: (734) 593-6000
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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 5101014936 (MI)
Hospitalist Physician Taxonomy 208M00000X · Licence 5101014936 (MI)

Record details

NPI number1942300454
Entity typeIndividual (Type 1)
GenderMale
Credentials DO
Sole proprietorNo
NPI enumeratedSeptember 24, 2006
Last updated in NPPESSeptember 6, 2016

Medicare enrollment

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

Medicare specialtyHOSPITALIST
Also practisesINTERNAL MEDICINE
Medical schoolMICHIGAN STATE UNIVERSITY COLLEGE OF HUMAN MEDICINE
Graduated 2001 (25 years in practice)
Group practice Apogee Medical Group Michigan Pc — 44 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 patients109
Services billed 306 a service is one billed item, such as a visit, a test or a procedure
Average patient age77

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.

Colleagues at Apogee Medical Group Michigan PC

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 44 clinicians in the practice; 12 are shown here.

Other providers in Chelsea