Active NPI
Sebastian Niezen
- Gastroenterology Physician
- Boston, MA
National Provider Identifier
1265162291
On this page
Key facts
NPPES NPI Registry- Primary specialty
- Gastroenterology Physician
- License
- 3018049
- Practice address
- 330 Brookline Ave
Boston, MA 02215-5400 - Phone
- (617) 480-3735
- NPI assigned
- Jun 13, 2022
- Sex
- Male
- Sole proprietor
- Yes
NPPES NPI Registry
Registry information is reported by the provider to CMS and is not verified. About this source
Specialties & licenses 2
| Specialty (taxonomy) | Code | License | State | Primary |
|---|---|---|---|---|
| Gastroenterology Physician | 207RG0100X | 3018049 | MA | Primary |
| Internal Medicine Physician | 207R00000X | MT226639 | PA |
Addresses
Primary practice location
330 Brookline Ave
Boston, MA 02215-5400
Mailing address
330 Brookline Ave
Boston, MA 02215-5400
Phone (617) 480-3735
Medicare participation
Medicare enrollment files- Medicare fee-for-service enrollment
- Not listed in the public Medicare enrollment file
National Provider Directory
National Provider Directory- Medicare enrollment (NPD)
- Not enrolled
State licenses
| License | State | Type | Specialty |
|---|---|---|---|
| MT226639 | PA | MD | Internal Medicine Physician |
| 3018049 | MA | MD | Gastroenterology Physician |
NPI Registry JSON
The complete NPPES record for this NPI in the NPI Registry API format.
{
"created_epoch": "1655078400000",
"enumeration_type": "NPI-1",
"last_updated_epoch": "1751241600000",
"number": "1265162291",
"addresses": [
{
"country_code": "US",
"country_name": "United States",
"address_purpose": "MAILING",
"address_type": "DOM",
"address_1": "330 BROOKLINE AVE",
"city": "BOSTON",
"state": "MA",
"postal_code": "022155400",
"telephone_number": "617-480-3735"
},
{
"country_code": "US",
"country_name": "United States",
"address_purpose": "LOCATION",
"address_type": "DOM",
"address_1": "330 BROOKLINE AVE",
"city": "BOSTON",
"state": "MA",
"postal_code": "022155400",
"telephone_number": "617-480-3735"
}
],
"practiceLocations": [],
"basic": {
"last_name": "NIEZEN",
"first_name": "SEBASTIAN",
"sole_proprietor": "YES",
"sex": "M",
"enumeration_date": "2022-06-13",
"last_updated": "2025-06-30",
"certification_date": "2025-06-30",
"status": "A"
},
"taxonomies": [
{
"code": "207RG0100X",
"taxonomy_group": "",
"desc": "Internal Medicine, Gastroenterology",
"state": "MA",
"license": "3018049",
"primary": true
},
{
"code": "207R00000X",
"taxonomy_group": "",
"desc": "Internal Medicine",
"state": "PA",
"license": "MT226639",
"primary": false
}
],
"identifiers": [],
"endpoints": [],
"other_names": []
}Other providers in Boston, MA
Sources for this page
- NPPES NPI Registry (CMS): identity, addresses, specialties, licenses, identifiers and endpoints. Last updated by the provider on Jun 30, 2025; self-reported and not verified by CMS. Specialty names from the NUCC taxonomy.
- National Provider Directory (CMS): practice roles, locations, licenses, networks and endpoints.