Mark Francis Grenquist, DO
Internal Medicine Physician · Chelsea, MI
Mark Francis Grenquist, DO is an internal medicine physician with a practice address in Chelsea, Michigan, and NPI 1942300454, issued on Sep 24, 2006. Check the license (Michigan 5101014936, as entered in NPPES) on the Michigan Board of Medicine (LARA); the Medicare figures below come from public CMS files.
- Name
- Mark Francis Grenquist
- Credential
- DO
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 5101014936 MI
Self-reported in NPPES; status is on the state search - Practice location
- 775 S Main St, Chelsea, MI 48118
- Phone
- (734) 593-6000
- Enumerated
- Sep 24, 2006
- Record last updated
- Sep 6, 2016 (not updated in 10 years: call before relying on the address or phone)
- Medicaid IDs
- 1942300454 MI
4631106 MI - Medicare enrollment
- Enrolled (PECOS I20041015000099); accepts Medicare assignment
- Medical or professional school
- Michigan State University College Of Human Medicine, 2001
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 5,735 in Michigan → Look up another NPI →
Also registered at 775 S Main St
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Susan Aagenas, PTPhysical Therapist1215402680
- Latasha Allen, OTRPhysical Rehabilitation Occupational Therapist1851867949
- James Anderson, LLPClinical Social Worker1205000783
- Anne Apaza, CRNACertified Registered Nurse Anesthetist1639116106
- Judith Ashin, LMSWClinical Social Worker1134304355
- Robert Ayotte, P.A.Physician Assistant1184679748
Verify Mark Francis Grenquist in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMichigan Board of Medicine (LARA)
Search for license 5101014936Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
94% fewer Medicare Part D claims than the average internal medicine physician in 2024
194 Medicare Part D claims for 104 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. 12 claims were for opioids.
Most prescribed
- Metoprolol Tartrate22 claims
- Cefuroxime17 claims
- Levofloxacin14 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Bills Medicare through one group practice
- Apogee Medical Group Michigan PCMarshall, MI
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Mark Francis Grenquist among 5,735 internal medicine physician records in Michigan
Mark Francis Grenquist, DO is one of 5,735 internal medicine physician records with a practice address in Michigan. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 10% of them.
- NPI issued2006 · 10% of these records are older, 60% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 62% of these records are
- Graduated2001 · median 2006 among the 3,564 with a school on file
- Record last updated2016 · 54% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a Michigan practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
8 internal medicine physician records list a practice address in Chelsea
They are 8 of the 500 NPPES records with a practice address in Chelsea, and 5,735 internal medicine physician records in Michigan.
All 5,735 in Michigan → Every provider in Chelsea → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Shan Ansari, M.D.Chelsea, MI 481181720108152
- Sarah BurChelsea, MI 481181063730190
- Diane Howlin, M.D.Chelsea, MI 481181417964552
- Lynn Kriengkrairut, MDChelsea, MI 481181013595750
- Rebecca Patrias, MDChelsea, MI 481181760594899
- Rubens Ribeiro, M.D.Chelsea, MI 481181396935367
- Steven Yarows, MDChelsea, MI 481181275532087
- Tracey Alperin, MDBrighton, MI 481161609227958
Common questions
What is Mark Francis Grenquist, DO's NPI number?
Mark Francis Grenquist, DO's National Provider Identifier (NPI) is 1942300454, issued on Sep 24, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Mark Francis Grenquist, DO located?
The NPPES record lists a practice address at 775 S Main St, Chelsea, MI, 48118. Phone: (734) 593-6000. Providers update this record themselves, so call before visiting.
How can I verify Mark Francis Grenquist, DO's license?
NPPES lists Michigan license number 5101014936, as entered by the provider. Search the Michigan Board of Medicine (LARA) at https://aca-prod.accela.com/MILARA/GeneralProperty/PropertyLookUp.aspx?isLicensee=Y&TabName=APO. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Mark Francis Grenquist, DO prescribe under Medicare Part D?
In 2024, Mark Francis Grenquist, DO had 194 Medicare Part D claims for 104 beneficiaries; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.