John Walker, D.O.
NPI 1851737811 · Internal Medicine Physician · Portland, ME
Enrolled with Medicare as Practitioner - Gastroenterology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
John Walker, D.O. is a Internal Medicine Physician provider in Portland, ME (NPI 1851737811).
Provider details
- NPI number
- 1851737811
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- D.O.
- Sex
- Male
- Sole proprietor
- No
- License
- DO2640 (ME)
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
13 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
344 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) |
|---|---|---|
| Removal of Polyps Or Growths of Large Bowel Using an Endoscope With Mechanical Snare45385 | 96 | $217 |
| Biopsy of Large Bowel Using a Flexible Endoscope45380 | 65 | $46 |
| Biopsy of Esophagus, Stomach, And/Or Upper Small Bowel Using a Flexible Endoscope43239 | 51 | $87 |
| Visit Complexity Inherent to Evaluation and Management Associated With Medical Care Services That Serve As the Continuing Focal Point for All Needed Health Care Services And/Or With Medical Care Services That Are Part of Ongoing Care Related to a Patient'SG2211 | 48 | $16 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 32 | $94 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 15 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Sodium Chloride/Nahco3/Kcl/Pegbrand: Peg 3350-Electrolyte | 307 | 299 |
| Omeprazole | 155 | 65 |
| Carvedilol | 59 | 11 |
| Pantoprazole Sodium | 55 | 17 |
| Sodium Chloride/Nahco3/Kcl/Pegbrand: Gavilyte-N | 43 | 41 |
| Budesonidebrand: Budesonide Dr | 23 | 12 |
| Mesalamine | 22 |
Practice location
Mailing address
Registry dates
- Enumerated
- 2013-05-17
- Last updated
- 2016-06-21
Frequently asked questions
- What is John Walker's NPI number?
- John Walker's National Provider Identifier (NPI) is 1851737811, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is John Walker's specialty?
- John Walker is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is John Walker located?
- John Walker's practice location on file with NPPES is 22 Bramhall St, Portland, ME 04102-3134.
- What is John Walker's phone number?
- The practice phone number listed in the NPPES registry for John Walker is (207) 662-6562.
- Does John Walker accept Medicare?
- John Walker is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is John Walker's NPI active?
- Yes — John Walker's NPI (1851737811) is active in the NPPES registry as of the last update on 2016-06-21.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.