Nathan Gwilliam, MD
NPI 1366882409 · Psychiatry Physician · New Haven, CT
Enrolled with Medicare as Practitioner - Psychiatry · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Nathan Gwilliam, MD is a Psychiatry Physician provider in New Haven, CT (NPI 1366882409).
Provider details
- NPI number
- 1366882409
- Entity type
- Individual
- Primary specialty
- Psychiatry PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- Yes
- License
- 71782 (CT)
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
12 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
21 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) |
|---|---|---|
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 21 | $148 |
Typical Medicare-allowed amounts for these services range $148–$148 (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.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 10 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Trazodone Hcl | 28 | 14 |
| Duloxetine Hcl | 21 | 12 |
| Lamotrigine | 20 | — |
| Lorazepam | 20 | — |
| Clonazepam | 18 | — |
| Fluoxetine Hcl | 18 | — |
| Bupropion Hclbrand: Bupropion Xl | 17 |
Practice location
Mailing address
Registry dates
- Enumerated
- 2013-07-03
- Last updated
- 2026-04-06
- Certified
- 2026-04-06
Frequently asked questions
- What is Nathan Gwilliam's NPI number?
- Nathan Gwilliam's National Provider Identifier (NPI) is 1366882409, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Nathan Gwilliam's specialty?
- Nathan Gwilliam is listed in the NPPES registry with a primary specialty of Psychiatry Physician (Allopathic & Osteopathic Physicians).
- Where is Nathan Gwilliam located?
- Nathan Gwilliam's practice location on file with NPPES is 389 Whitney Ave, New Haven, CT 06511.
- What is Nathan Gwilliam's phone number?
- The practice phone number listed in the NPPES registry for Nathan Gwilliam is (203) 293-6258.
- Does Nathan Gwilliam accept Medicare?
- Nathan Gwilliam is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Nathan Gwilliam's NPI active?
- Yes — Nathan Gwilliam's NPI (1366882409) is active in the NPPES registry as of the last update on 2026-04-06.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.