Mark H. Johnston, MD
NPI 1003898131ActiveIndividual· Internal Medicine, Gastroenterology· Lancaster, PA
Internal Medicine, Gastroenterology (MD) in Lancaster, Pennsylvania, trained at Hahnemann University College of Medicine (class of 1985). 339 Medicare patients in 2024, $133,380 paid; nearly all of their 458 Part D prescriptions were generic (95%). Abbvie Inc. was the largest of 13 companies reporting payments in 2025, $577.51 in all, mostly food and beverage.
Overview
| NPI | 1003898131 |
|---|---|
| Status | Active |
| Entity type | Individual |
| Credential | MD |
| Sole proprietor | No |
| NPI issued | Nov 15, 2005 |
| Last updated in NPPES | Jun 13, 2019 |
Specialties and licenses
| Taxonomy | Code | License | State |
|---|---|---|---|
| Internal Medicine, Gastroenterology Primary | 207RG0100X | MD425522 | PA |
Exclusion screening
| List | Result | Details |
|---|---|---|
| HHS-OIG LEIE · Oct 9, 2026 | No match | Checked by NPI and by name + state |
| North Carolina Medicaid · Nov 4, 2026 | No match | — |
| New York OMIG · Nov 4, 2026 | No match | — |
| Ohio Medicaid · Nov 4, 2026 | No match | — |
| Pennsylvania Medicheck · Nov 4, 2026 | No match | — |
| Washington HCA · Nov 4, 2026 | No match | — |
Official OIG search · How matching works ·Bulk check a roster
Medicare
| Enrollment (PECOS) | Enrolled Practitioner - Gastroenterology (PA) |
|---|---|
| Accepts assignment | Yes (participating) |
Medicare services in 2024
| Medicare patients | 339 |
|---|---|
| Services billed | 4,420 across 41 procedure codes |
| Paid by Medicare | $133,380 |
Part D prescriptions in 2024
| Prescriptions (claims) | 458 · 1,122 30-day fills |
|---|---|
| Patients | 155 |
| Total drug cost | $40,177 |
| Generic share | 95% of claims |
Education and affiliations
| Medical school | Hahnemann University College of Medicine |
|---|---|
| Graduation year | 1985 |
| Medicare specialty | Gastroenterology |
Medical groups
- Lancaster General HospitalLancaster, PA · 520 clinicians
- Regional Gastroenterology Associates of Lancaster, Ltd.Lancaster, PA · 244 clinicians
Hospital affiliation
- Lancaster General HospitalLancaster, PA
Industry payments (Open Payments)
- 2025$577.51 · 27 payments from 13 companies
- 2024$689.54 · 32 payments from 10 companies
Top paying companies in 2025
| Company | Amount | Payments |
|---|---|---|
| Abbvie Inc. | $169.39 | 8 |
| Ardelyx, Inc. | $109.25 | 4 |
| Salix Pharmaceuticals, A Division of Bausch Health US, LLC | $61.31 | 3 |
| Janssen Biotech, Inc. | $56.02 | 2 |
| Genzyme Corporation | $26.50 | 1 |
What the 2025 payments were for
- Food and Beverage$577.51 · 27 payments
Receiving payments does not imply wrongdoing. What Open Payments covers ·original records
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