NPPES file of Aug 9, 2026

Mary C. O'Brien, M.D.

Internal Medicine Physician · Shrewsbury, MA

Mary C. O'Brien, M.D. is an internal medicine physician with a practice address in Shrewsbury, Massachusetts, and NPI 1912980434, issued on Nov 29, 2005. Check the license (Massachusetts 79570, as entered in NPPES) on the Massachusetts Board of Registration in Medicine; the Medicare figures below come from public CMS files.

Record from CMS NPPES, file of Aug 9, 2026 · Medicare files 2024 · method · Verify with CMS →

NPPES recordNPPES file of Aug 9, 2026
1912980434
Name
Mary C. O'Brien
Credential
M.D.
Primary taxonomy
Internal Medicine Physician 207R00000X
License number
79570 MA
Self-reported in NPPES; status is on the state search
Practice location
604 Main St, Shrewsbury, MA 01545
Phone
(508) 842-0057
Enumerated
Nov 29, 2005
Record last updated
Nov 25, 2020 (not updated in 6 years: call before relying on the address or phone)
Medicaid ID
3124177 MA
Medicare enrollment
Enrolled (PECOS I20050503001259); accepts Medicare assignment
Medical or professional school
State University Of New York At Stony Brook, School Of Medicine, 1991
Telehealth
Offers telehealth (CMS)
Entity
Type 1 · individual
Public record from CMS NPPES (open it on the CMS NPI Registry). Enrollment, assignment, school and telehealth: CMS Doctors and Clinicians file, Aug 2026. A record is not a license: verify it with the state board.
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8 nearest internal medicine physician records → All 6,825 in Massachusetts → Look up another NPI →

Also registered at 604 Main St

A shared address usually means a shared clinic or building; it does not show who employs whom.

  1. David Ahern, M.D.Family Medicine Physician1720425598
  2. June Blanco, M.D.Internal Medicine Physician1548242787
  3. Vasilios Chrisostomidis, D.O.Family Medicine Physician1669458048
  4. Nicole DaluzNurse Practitioner1891367405
  5. Frank Domino, M.D.Family Medicine Physician1942283809
  6. Heather Gallo, M.D.Internal Medicine Physician1326021189

Verify Mary C. O'Brien in five checks

  1. 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
  2. 2LicenseActive license and public ordersMassachusetts Board of Registration in Medicine
    Search for license 79570    Check the board
  3. 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
  4. 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
  5. 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
Open the Massachusetts license search

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36% more Medicare Part D claims than the average internal medicine physician in 2024

4,309 Medicare Part D claims for 368 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D. 123 claims were for opioids.

  1. Mary O'Brien4,309
  2. Specialty average3,176

Most prescribed

  1. Atorvastatin Calcium387 claims
  2. Losartan Potassium230 claims
  3. Rosuvastatin Calcium213 claims
  4. Levothyroxine Sodium174 claims
  5. Lisinopril169 claims
  6. Lorazepam136 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

  1. Umass Memorial Medical Group IncShrewsbury, MA

Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).

Mary C. O'Brien among 6,825 internal medicine physician records in Massachusetts

Mary C. O'Brien, M.D. is one of 6,825 internal medicine physician records with a practice address in Massachusetts. 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, 88% newer
  • In a Medicare fileYes · 75% of these records are
  • In the CMS Doctors and Clinicians fileYes · 60% of these records are
  • Graduated1991 · median 2004 among the 4,103 with a school on file
  • Record last updated2020 · 64% 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 Massachusetts practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).

28 internal medicine physician records list a practice address in Shrewsbury

They are 28 of the 550 NPPES records with a practice address in Shrewsbury, and 6,825 internal medicine physician records in Massachusetts.

All 6,825 in Massachusetts → Every provider in Shrewsbury → Internal Medicine Physician nationwide →

The 8 internal medicine physician records with the nearest ZIP codes

  1. Sarika Aggarwal, M.D.Shrewsbury, MA 015451265415236
  2. Durga Bathini, M.D.Shrewsbury, MA 015451093798076
  3. June Blanco, M.D.Shrewsbury, MA 015451548242787
  4. Heather Gallo, M.D.Shrewsbury, MA 015451326021189
  5. Deborah Hazen, M.D.Shrewsbury, MA 015451427038645
  6. Preeti Jain, MDShrewsbury, MA 015451801860192
  7. Afroz Saquib, M.D.Shrewsbury, MA 015451558344457
  8. Sapna Savant, MDShrewsbury, MA 015451235100629

Common questions

What is Mary C. O'Brien, M.D.'s NPI number?

Mary C. O'Brien, M.D.'s National Provider Identifier (NPI) is 1912980434, issued on Nov 29, 2005. An NPI identifies a provider in billing; it is not a license.

Where is Mary C. O'Brien, M.D. located?

The NPPES record lists a practice address at 604 Main St, Shrewsbury, MA, 01545. Phone: (508) 842-0057. Providers update this record themselves, so call before visiting.

How can I verify Mary C. O'Brien, M.D.'s license?

NPPES lists Massachusetts license number 79570, 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 Mary C. O'Brien, M.D. prescribe under Medicare Part D?

In 2024, Mary C. O'Brien, M.D. had 4,309 Medicare Part D claims for 368 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.

Written with AI tools from the named public files; every figure is computed from those files (how it is made).

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.