Justin Larson, M.D.
NPI 1821319393 · Emergency Medicine Physician · Cambridge, MA
Enrolled with Medicare as Practitioner - Emergency Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Justin Larson, M.D. is a Emergency Medicine Physician provider in Cambridge, MA (NPI 1821319393).
Provider details
- NPI number
- 1821319393
- Entity type
- Individual
- Primary specialty
- Emergency Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- Yes
- License
- 266658 (MA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
16 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
47 Medicare services, 2024 (ranked within specialty)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Emergency Department Visit With Moderate Level of Medical Decision Making99284 | 26 | $127 |
| Emergency Department Visit With High Level of Medical Decision Making99285 | 21 | $183 |
Typical Medicare-allowed amounts for these services range $127–$183 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, not a price quote and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
Practice location
Mailing address
Registry dates
- Enumerated
- 2010-06-18
- Last updated
- 2020-12-20
- Certified
- 2020-12-20
Frequently asked questions
- What is Justin Larson's NPI number?
- Justin Larson's National Provider Identifier (NPI) is 1821319393, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Justin Larson's specialty?
- Justin Larson is listed in the NPPES registry with a primary specialty of Emergency Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Justin Larson located?
- Justin Larson's practice location on file with NPPES is 1493 Cambridge St, Cambridge, MA 02139-1099.
- What is Justin Larson's phone number?
- The practice phone number listed in the NPPES registry for Justin Larson is (617) 665-1000.
- Does Justin Larson accept Medicare?
- Justin Larson is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Justin Larson's NPI active?
- Yes — Justin Larson's NPI (1821319393) is active in the NPPES registry as of the last update on 2020-12-20.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.