Mark Joseph O'Connor, M.D.
Endocrinology, Diabetes & Metabolism Physician · Worcester, MA
Mark Joseph O'Connor, M.D. is an endocrinology, diabetes & metabolism physician with a practice address in Worcester, Massachusetts, and NPI 1518300284, issued on Apr 12, 2013. Check the license (Massachusetts 266640, as entered in NPPES) on the Massachusetts Board of Registration in Medicine; the Medicare figures below come from public CMS files.
- Name
- Mark Joseph O'Connor
- Credential
- M.D.
- Primary taxonomy
- Endocrinology, Diabetes & Metabolism Physician 207RE0101X
- License number
- 266640 MA
Self-reported in NPPES; status is on the state search - Practice location
- 55 Lake Ave N, Worcester, MA 01655
- Phone
- (508) 334-3206
- Enumerated
- Apr 12, 2013
- Record last updated
- Mar 30, 2021 (not updated in 5 years: call before relying on the address or phone)
- Fax
- (774) 442-4668
- Medicare enrollment
- Enrolled (PECOS I20161019001933); accepts Medicare assignment
- Medical or professional school
- University Of Massachusetts Medical School, 2013
- Telehealth
- Offers telehealth (CMS)
- Entity
- Type 1 · individual
8 nearest endocrinology, diabetes & metabolism physician records → All 522 in Massachusetts → Look up another NPI →
Also registered at 55 Lake Ave N
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Mary-Alice Abbott, MDClinical Genetics (M.D.) Physician1982799417
Verify Mark Joseph O'Connor in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMassachusetts Board of Registration in Medicine
Search for license 266640Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
50% more Medicare Part D claims than the average endocrinology, diabetes & metabolism physician in 2024
3,953 Medicare Part D claims for 487 beneficiaries, against an average of 2,630 among the 8,223 providers of this specialty who prescribed in Part D. Brand-name drugs were 57% of claims.
Most prescribed
- Ozempic381 claims
- Trulicity365 claims
- Jardiance338 claims
- Metformin Hcl Er272 claims
- Glipizide Er200 claims
- Metformin Hcl196 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.
The MIPS final score for 2023 (Medicare payment program): 97 of 100
The Merit-based Incentive Payment System score is reported for this clinician. Four categories are weighted into the final score; the average among 454,083 clinicians with a measured score was 83.5.
Source: CMS Quality Payment Program, MIPS performance year 2023; category weights for 2023 (qpp.cms.gov).
Bills Medicare through one group practice
- Umass Memorial Medical Group IncWorcester, MA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Mark Joseph O'Connor among 522 endocrinology, diabetes & metabolism physician records in Massachusetts
Mark Joseph O'Connor, M.D. is one of 522 endocrinology, diabetes & metabolism physician records with a practice address in Massachusetts. 82% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2013, is newer than 75% of them.
- NPI issued2013 · 75% of these records are older, 20% newer
- In a Medicare fileYes · 82% of these records are
- In the CMS Doctors and Clinicians fileYes · 72% of these records are
- Graduated2013 · median 2002 among the 378 with a school on file
- Record last updated2021 · 60% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207RE0101X and a Massachusetts practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Endocrinology, Diabetes & Metabolism Physician providers in Massachusetts
There are 522 endocrinology, diabetes & metabolism physician records in Massachusetts.
All 522 in Massachusetts → Every provider in Worcester → Endocrinology, Diabetes & Metabolism Physician nationwide →
The 8 endocrinology, diabetes & metabolism physician records with the nearest ZIP codes
- Neil Aronin, M.D.Worcester, MA 016551679556252
- Seth Arum, M.D.Worcester, MA 016551679578793
- Daniel Baran, M.D.Worcester, MA 016551841260221
- Raffaella Colzani, M.D.Worcester, MA 016551356324297
- Taniya De Silva, M.D.Worcester, MA 016551740212273
- Leslie Domalik, MDWorcester, MA 016551841307261
- Richard Haas, M.D.Worcester, MA 016551023017373
- Samir Malkani, M.D.Worcester, MA 016551174506018
Common questions
What is Mark Joseph O'Connor, M.D.'s NPI number?
Mark Joseph O'Connor, M.D.'s National Provider Identifier (NPI) is 1518300284, issued on Apr 12, 2013. An NPI identifies a provider in billing; it is not a license.
Where is Mark Joseph O'Connor, M.D. located?
The NPPES record lists a practice address at 55 Lake Ave N, Worcester, MA, 01655. Phone: (508) 334-3206. Providers update this record themselves, so call before visiting.
How can I verify Mark Joseph O'Connor, M.D.'s license?
NPPES lists Massachusetts license number 266640, as entered by the provider. Search the Massachusetts Board of Registration in Medicine at https://findmydoctor.mass.gov/. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Mark Joseph O'Connor, M.D. prescribe under Medicare Part D?
In 2024, Mark Joseph O'Connor, M.D. had 3,953 Medicare Part D claims for 487 beneficiaries; the average among endocrinology, diabetes & metabolism physician prescribers was 2,630. Part D covers Medicare prescriptions only.
What is Mark Joseph O'Connor, M.D.'s MIPS final score?
The 2023 MIPS final score is 97 of 100. The average among 454,083 clinicians with a measured score was 83.5.
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.