Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

John Walker, DO

Individual provider Internal Medicine Physician · NPI 1851737811

John Walker, DO practises Gastroenterology in Portland, Maine. Qualified in 2013, 13 years ago. Practices with Mainehealth, a 2,615-clinician group and accepts Medicare assignment. Licensed in Maine.

Years since qualifying
13
Licensed in
ME
In the registry since
2013
What do these letters mean?
DO — Doctor of Osteopathic Medicine
A fully licensed physician, trained like an MD with additional musculoskeletal training. Equivalent practice rights in all 50 states.

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Practice location Address checks out

22 Bramhall St
Portland, ME 04102-3134 Not confirmed with CMS for 10 years — call before visiting
Phone: (207) 662-6562
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Internal Medicine Physician (primary) Taxonomy 207R00000X · Licence DO2640 (ME)

Record details

NPI number1851737811
Entity typeIndividual (Type 1)
GenderMale
Credentials DO
Sole proprietorNo
NPI enumeratedMay 17, 2013
Last updated in NPPESJune 21, 2016

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyGASTROENTEROLOGY
Also practisesINTERNAL MEDICINE
Medical schoolOTHER
Graduated 2013 (13 years in practice)
Group practice Mainehealth — 2615 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations3 on file with Medicare

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Upper gastrointestinal (GI) endoscopy for acid reflux 98 times · 76th percentile
Colonoscopy 78 times · 74th percentile

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

Medicare patients and services, 2024

From the CMS Medicare Physician & Other Practitioners file for calendar year 2024. It counts Original Medicare patients only, so a practice that mostly sees Medicare Advantage or privately insured patients looks smaller here than it is.

Medicare patients242
Services billed 445 a service is one billed item, such as a visit, a test or a procedure
Average patient age71

Dollar amounts are not shown. What Medicare pays a practice is gross billings, before staff, premises and tax and including the cost of any drugs it administers, so it is not what a clinician earns.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at Mainehealth

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 2615 clinicians in the practice; 12 are shown here.

Other providers in Portland