Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
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Dr. Margarita C Castro-Zarraga, MD

Individual provider Family Medicine Physician · NPI 1578705679

Dr. Margarita C Castro-Zarraga, MD is registered under Family Practice in Lowell, Massachusetts. Qualified in 2005, 21 years ago. Practices with Concord Medical Group PLLC, a 193-clinician group, works from 2 locations and accepts Medicare assignment. Licensed in Massachusetts.

Years since qualifying
21
Licensed in
MA
In the registry since
2009
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

161 Jackson St
Lowell, MA 01852-2103
Phone: (978) 937-9700
Fax: (978) 221-6728
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Additional practice locations (1)

  • 275 Nichols Rd, Fitchburg, MA 01420-1919 — (978) 878-8300

Specialties & licences

Family Medicine Physician (primary) Taxonomy 207Q00000X · Licence 251722 (MA)

Record details

NPI number1578705679
Entity typeIndividual (Type 1)
GenderFemale
Credentials MD
Sole proprietorNo
NPI enumeratedApril 3, 2009
Last updated in NPPESJanuary 3, 2024
Certification dateJanuary 3, 2024

Medicare enrollment

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

Medicare specialtyFAMILY PRACTICE
Medical schoolOTHER
Graduated 2005 (21 years in practice)
Group practice Concord Medical Group Pllc — 193 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations4 on file with Medicare

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 patients31
Services billed 46 a service is one billed item, such as a visit, a test or a procedure
Average patient age68

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.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Food and Beverage $63 3 payments · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician. Those with a page here are linked.

Colleagues at Concord Medical Group PLLC

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 193 clinicians in the practice; 12 are shown here.

Other providers in Lowell