Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Justin Granstein, MD

Neurology Physician in Boston, MA · enumerated 2015.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1699169599

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Registry record

Entity type Individual (Type 1)

Name Dr. Justin Granstein

Credential MD

Sex Male

Practice address 110 Francis St Ste 3b, Boston, MA, 02215

Phone (617) 632-7246

Enumeration date Mar 27, 2015

Last updated in NPPES Jul 20, 2023

Taxonomy & licenses

2084A2900X Neurocritical Care Physician Allopathic & Osteopathic Physicians · License 1015998 (MA) Secondary

2084N0400X Neurology Physician Allopathic & Osteopathic Physicians · License 1015998 (MA) Primary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

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Frequently asked questions

Is this the official NPI registry?

No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.

What specialty is Justin Granstein?

Justin Granstein is registered in NPPES with the primary taxonomy of Neurology Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2023-07-20.