Gunnlaugur Petur Nielsen, MD

Primary specialty

Anatomic Pathology PhysicianTaxonomy code 207ZP0101X

License

78780 Issued in MA

Practice address

55 Fruit St WRN 2
Pathology Associates
Boston, MA 02114-2696

Phone

(617) 724-1469

Fax

(617) 726-9312

NPI assigned

Mar 16, 2006

Sex

Male

Sole proprietor

No

Registry information is reported by the provider to CMS and is not verified. About this source

Specialties & licenses 1

Addresses

Other identifiers 3

Medicare fee-for-service enrollment

Enrolled in MA

Eligible to order & refer

• Part B services: Yes
• Medical equipment: Yes
• Home health: Yes
• Power mobility devices: Yes
• Hospice: Yes

Green means eligible to order or refer.

Enrollment records 1

Specialty

Pathology

Education

Other, 1988

Medicare assignment

Accepts the Medicare-approved amount as payment in full

Group practices

Massachusetts General Physicians Organization IncGroup PAC ID 2466365820, 3,494 clinicians

Practice addresses (Care Compare)

Hospital & facility affiliations

• Massachusetts General Hospital Hospital, Boston, MA, CCN 220071
• Martha'S Vineyard Hospital Inc Hospital, Oak Bluffs, MA, CCN 221300
• Massachusetts Eye and Ear Infirmary - Hospital, Boston, MA, CCN 220075
• Nantucket Cottage Hospital Hospital, Nantucket, MA, CCN 220177

Medicare enrollment (NPD)

Enrolled

Credentials

Doctor of Medicine

State licenses

Practice roles

Locations

Interoperability endpoints

• Direct secure messaging: nielsen.gunnlaugur.mgh@direct.partners.masshiway.net

Organizations this provider is connected to: Medicare benefit reassignments (the organization bills Medicare for this provider’s services), Care Compare group memberships and National Provider Directory roles.

• Massachusetts General Physicians Organization Inc

  • Dermatology Physician
  • Boston, MA
  • NPI 1801874573
  Medicare reassignment Care Compare group
• The General Hospital Corporation

  • General Acute Care Hospital
  • Boston, MA
  • NPI 1023049236
  Medicare reassignment NPD
• General Hospital Corp

  • General Acute Care Hospital
  • Boston, MA
  • NPI 1508390014
  NPD

Hospitals and other facilities this clinician is affiliated with according to Medicare Care Compare.

• Martha'S Vineyard Hospital, Inc.

  • Critical Access Hospital
  • Oak Bluffs, MA
  • NPI 1134206386
  Care Compare affiliation
• Massachusetts Eye and Ear Infirmary

  • General Acute Care Hospital
  • Boston, MA
  • NPI 1639101751
  Care Compare affiliation
• Nantucket Cottage Hospital

  • Rural Acute Care Hospital
  • Nantucket, MA
  • NPI 1447214622
  Care Compare affiliation
• The General Hospital Corporation

  • General Acute Care Hospital
  • Boston, MA
  • NPI 1023049236
  Care Compare affiliation

The complete NPPES record for this NPI in the NPI Registry API format.

{
    "created_epoch": "1142467200000",
    "enumeration_type": "NPI-1",
    "last_updated_epoch": "1783900800000",
    "number": "1174592653",
    "addresses": [
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "MAILING",
            "address_type": "DOM",
            "address_1": "PO BOX 9142",
            "address_2": "MASS GENERAL PHYSICIAN ORGANIZATION",
            "city": "CHARLESTOWN",
            "state": "MA",
            "postal_code": "021299142",
            "telephone_number": "617-724-0287",
            "fax_number": "617-726-2894"
        },
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "LOCATION",
            "address_type": "DOM",
            "address_1": "55 FRUIT ST WRN 2",
            "address_2": "PATHOLOGY ASSOCIATES",
            "city": "BOSTON",
            "state": "MA",
            "postal_code": "021142696",
            "telephone_number": "617-724-1469",
            "fax_number": "617-726-9312"
        }
    ],
    "practiceLocations": [
        {
            "address_1": "75 Francis St",
            "address_purpose": "LOCATION",
            "city": "Boston",
            "state": "MA",
            "postal_code": "021156110",
            "country_code": "US",
            "telephone_number": "617-732-5500",
            "country_name": "United States",
            "address_type": "DOM"
        }
    ],
    "basic": {
        "last_name": "NIELSEN",
        "first_name": "GUNNLAUGUR",
        "middle_name": "PETUR",
        "name_prefix": "Dr.",
        "credential": "MD",
        "sole_proprietor": "NO",
        "sex": "M",
        "enumeration_date": "2006-03-16",
        "last_updated": "2026-07-13",
        "certification_date": "2026-06-12",
        "status": "A"
    },
    "taxonomies": [
        {
            "code": "207ZP0101X",
            "taxonomy_group": "",
            "desc": "Pathology, Anatomic Pathology",
            "state": "MA",
            "license": "78780",
            "primary": true
        }
    ],
    "identifiers": [
        {
            "code": "05",
            "desc": "MEDICAID",
            "issuer": null,
            "identifier": "3124584",
            "state": "MA"
        },
        {
            "code": "01",
            "desc": "Other (non-Medicare)",
            "issuer": "BCBS MA",
            "identifier": "J30551",
            "state": "MA"
        },
        {
            "code": "01",
            "desc": "Other (non-Medicare)",
            "issuer": "TUFTS HEALTH PLAN",
            "identifier": "078780",
            "state": "MA"
        }
    ],
    "endpoints": [],
    "other_names": []
}

• Yunan Nie, MD
• Elizabeth Anne Niedzwiecki, MSW
• Megan Niegisch
• Henry M Nields, MD, PHD
• Heidi Beth Niell, PAC
• Heber C Nielsen, MD
• Sarah Nielsen, LICSW
• Julie Anne Niemi, LICSW
• Andrew Alan Nierenberg, MD
• Natalie E. Nierenberg, MD

• Anatomic Pathology Physician in Boston, MA
• Providers in Boston, MA by specialty
• Anatomic Pathology Physician in Massachusetts

• NPPES NPI Registry (CMS): identity, addresses, specialties, licenses, identifiers and endpoints. Last updated by the provider on Jul 13, 2026; self-reported and not verified by CMS. Specialty names from the NUCC taxonomy.
• Medicare enrollment (CMS PECOS): enrollments, PAC IDs and benefit reassignments; Order and Referring.
• Medicare Care Compare (CMS): clinician profile, group practices, facility affiliations, MIPS scores and star ratings.
• National Provider Directory (CMS): practice roles, locations, licenses, networks and endpoints.

Verify at the official NPI Registry.