Mark T. O'Brien, D.O.
Family Medicine Physician · Saint Clair, MI
Mark T. O'Brien, D.O. is a family medicine physician with a practice address in Saint Clair, Michigan, and NPI 1255322509, issued on Nov 3, 2005. Check the license (Michigan 5101009744, as entered in NPPES) on the Michigan Board of Medicine (LARA); the Medicare figures below come from public CMS files.
- Name
- Mark T. O'Brien
- Credential
- D.O.
- Primary taxonomy
- Family Medicine Physician 207Q00000X
- License number
- 5101009744 MI
Self-reported in NPPES; status is on the state search - Practice location
- 1280 S 9TH St, Saint Clair, MI 48079
- Phone
- (810) 326-0837
- Enumerated
- Nov 3, 2005
- Record last updated
- Feb 25, 2022
- Fax
- (810) 326-1534
- Medicaid ID
- 2662631 MI
- Entity
- Type 1 · individual
8 nearest family medicine physician records → All 6,013 in Michigan → Look up another NPI →
Verify Mark T. O'Brien in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMichigan Board of Medicine (LARA)
Search for license 5101009744Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
18% more Medicare Part D claims than the average family medicine physician in 2024
4,182 Medicare Part D claims for 296 beneficiaries, against an average of 3,544 among the 117,163 providers of this specialty who prescribed in Part D. Brand-name drugs were 11% of claims. 316 claims were for opioids.
Most prescribed
- Atorvastatin Calcium209 claims
- Hydrocodone-Acetaminophen190 claims
- Levothyroxine Sodium188 claims
- Alprazolam109 claims
- Amlodipine Besylate103 claims
- Gabapentin102 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.
Mark T. O'Brien among 6,013 family medicine physician records in Michigan
Mark T. O'Brien, D.O. is one of 6,013 family medicine physician records with a practice address in Michigan. 75% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 89% newer
- In a Medicare fileYes · 75% of these records are
- In the CMS Doctors and Clinicians fileNo · 58% of these records are
- Record last updated2022 · 58% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207Q00000X and a Michigan practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
3 family medicine physician records list a practice address in Saint Clair
They are 3 of the 117 NPPES records with a practice address in Saint Clair, and 6,013 family medicine physician records in Michigan.
All 6,013 in Michigan → Every provider in Saint Clair → Family Medicine Physician nationwide →
The 8 family medicine physician records with the nearest ZIP codes
- Dawn Lambrecht, MDSaint Clair, MI 480791356317317
- Laura Lucio-Reincke, M.D.Saint Clair, MI 480791851392930
- Kenneth Bollin, MDSaint Clair Shores, MI 480801144212788
- Margaret Eckel, D.O.St Clair Shores, MI 480801144212325
- Kathleen Fulgenzi, MDSt Clair Shores, MI 480801588656102
- Donna Hoban, M.D.St Clair Shores, MI 480801205828498
- Mark Holowinski, M.D.Saint Clair Shores, MI 480801023010063
- Sigmund McIntyre, MDSaint Clair Shores, MI 480801275525966
Common questions
What is Mark T. O'Brien, D.O.'s NPI number?
Mark T. O'Brien, D.O.'s National Provider Identifier (NPI) is 1255322509, issued on Nov 3, 2005. An NPI identifies a provider in billing; it is not a license.
Where is Mark T. O'Brien, D.O. located?
The NPPES record lists a practice address at 1280 S 9TH St, Saint Clair, MI, 48079. Phone: (810) 326-0837. Providers update this record themselves, so call before visiting.
How can I verify Mark T. O'Brien, D.O.'s license?
NPPES lists Michigan license number 5101009744, 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 T. O'Brien, D.O. prescribe under Medicare Part D?
In 2024, Mark T. O'Brien, D.O. had 4,182 Medicare Part D claims for 296 beneficiaries; the average among family medicine physician prescribers was 3,544. 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.