John Warren, MD
NPI 1386634400 · Ophthalmology Physician · Greenfield, MA
Enrolled with Medicare as Practitioner - Ophthalmology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
John Warren, MD is a Ophthalmology Physician provider in Greenfield, MA (NPI 1386634400).
Provider details
- NPI number
- 1386634400
- Entity type
- Individual
- Primary specialty
- Ophthalmology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- 223233 (MA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure25% of score
20 yrs in NPPES registry
- Profile completeness25% of score
100% of core fields populated
- Practice footprint15% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)25% of score
3,913 Medicare services, 2024 (ranked within specialty)
- Open Payments transparency10% of score
Has Open Payments disclosures (2024)
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 .
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) |
|---|---|---|
| Measurement of Corneal Curvature and Depth of Eye92136 | 987 | $28 |
| Removal of Cataract With Insertion of Prosthetic Lens66984 | 619 | $561 |
| Imaging of Retina92134 | 542 | $42 |
| Established Patient Complete Exam of Visual System92014 | 538 | $135 |
| Ct Scan of Cornea92025 | 333 | $39 |
| Insertion of Drug Delivery Implant Into Tear Duct of Eye68841 | 213 | $17 |
| New Patient Office Or Other Outpatient Visit With Moderate Level of Medical Decision Making, If Using Time, 45 Minutes Or More |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 16 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Ketorolac Tromethamine | 1,339 | 709 |
| Prednisolone Acetate | 513 | 321 |
| Latanoprost | 212 | 72 |
| Brimonidine Tartrate | 94 | 33 |
| Timolol Maleate | 56 | 20 |
| Dorzolamide Hcl/Timolol Maleatbrand: Dorzolamide-Timolol | 53 | 22 |
| Fluorometholone | 52 | 17 |
| Erythromycin Base |
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$1,237 across 23 records (Open Payments 2024)
Open Payments discloses payments and transfers of value (meals, travel, consulting, research, royalties) from drug and device makers to providers. This is a transparency signal, not a verdict — such payments are legal and common, and their presence is neither an endorsement nor a criticism. Source: CMS Open Payments, program year 2024.
Practice location
Mailing address
Registry dates
- Enumerated
- 2005-10-28
- Last updated
- 2023-03-07
Frequently asked questions
- What is John Warren's NPI number?
- John Warren's National Provider Identifier (NPI) is 1386634400, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is John Warren's specialty?
- John Warren is listed in the NPPES registry with a primary specialty of Ophthalmology Physician (Allopathic & Osteopathic Physicians).
- Where is John Warren located?
- John Warren's practice location on file with NPPES is 33 Riddell St, Greenfield, MA 01301.
- What is John Warren's phone number?
- The practice phone number listed in the NPPES registry for John Warren is (413) 774-7016.
- Does John Warren accept Medicare?
- John Warren is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is John Warren's NPI active?
- Yes — John Warren's NPI (1386634400) is active in the NPPES registry as of the last update on 2023-03-07.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.