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

Mark H Johnston, MD

Individual provider Gastroenterology Physician · NPI 1003898131

Mark H Johnston, MD practises Gastroenterology in Lancaster, Pennsylvania. Graduated from Hahnemann University College of Medicine in 1985, 41 years ago. Practices with Regional Gastroenterology Associates of Lancaster, Ltd, a 251-clinician group and accepts Medicare assignment. Licensed in Pennsylvania.

Years since qualifying
41
Trained at
Hahnemann University College of Medicine
Licensed in
PA
In the registry since
2005
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

2112 Harrisburg Pike Ste 202
Lancaster, PA 17601-2644
Phone: (717) 544-3500
Fax: (717) 544-3501
Show map & directions

Directions in Google Maps · Apple Maps · OpenStreetMap

Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Gastroenterology Physician (primary) Taxonomy 207RG0100X · Licence MD425522 (PA)

Record details

NPI number1003898131
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedNovember 15, 2005
Last updated in NPPESJune 13, 2019

Medicare enrollment

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

Medicare specialtyGASTROENTEROLOGY
Medical schoolHAHNEMANN UNIVERSITY COLLEGE OF MEDICINE
Graduated 1985 (41 years in practice)
Group practice Regional Gastroenterology Associates Of Lancaster, Ltd. — 251 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations2 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 69 times · 69th percentile
Colonoscopy 52 times · 64th 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 patients339
Services billed 4,420 a service is one billed item, such as a visit, a test or a procedure
Average patient age73

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.

Payments from drug and device companies, 2025

Drug and device makers are required by federal law (the Physician Payments Sunshine Act) to report what they pay or give to clinicians, and CMS publishes the reports as Open Payments. This is the 2025 program year. A report is a record of a payment, not an allegation of anything, and many are small items such as meals. Only general payments are listed here; research payments and ownership or investment interests are reported separately by CMS and are not shown.

Food and Beverage $578 27 payments · a meal or drink at a meeting or visit, not a fee

Each amount is the sum of what companies reported for that kind of payment in 2025, rounded to the dollar. Not all of it is income to the clinician: a meal is not a fee, a charitable contribution goes to a charity, and a royalty or an acquisition payment is not a salary.

Check a report, or dispute one, at the source in CMS’s own tool, Open Payments. Corrections go through CMS’s dispute process. This site removes a home address on request and asks for no proof, because that is privacy; it will not remove an accurate payment report on request, because that is a statutory public disclosure.

Practises at

Facilities the CMS Facility Affiliation file lists for this clinician.

Colleagues at Regional Gastroenterology Associates of Lancaster, Ltd

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 251 clinicians in the practice; 12 are shown here.

Other providers in Lancaster