Mark Johnston, MD
NPI 1003898131 · Gastroenterology Physician · Lancaster, PA
Enrolled with Medicare as Practitioner - Gastroenterology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Johnston, MD is a Gastroenterology Physician provider in Lancaster, PA (NPI 1003898131).
Provider details
- NPI number
- 1003898131
- Entity type
- Individual
- Primary specialty
- Gastroenterology PhysicianAllopathic & Osteopathic Physicians
- Credential
- MD
- Sex
- Male
- Sole proprietor
- No
- License
- MD425522 (PA)
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
497 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) |
|---|---|---|
| Removal of Polyps Or Growths of Large Bowel Using an Endoscope With Mechanical Snare45385 | 102 | $238 |
| Biopsy of Large Bowel Using a Flexible Endoscope45380 | 99 | $97 |
| Biopsy of Esophagus, Stomach, And/Or Upper Small Bowel Using a Flexible Endoscope43239 | 71 | $97 |
| Established Patient Office Or Other Outpatient Visit With Low Level OD Decision Making, If Using Time, 20 Minutes Or More99213 | 46 | $86 |
| Established Patient Office Or Other Outpatient Visit With Moderate Level of Decision Making, If Using Time, 30 Minutes Or More99214 | 42 | $121 |
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 5 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Omeprazole | 219 | 76 |
| Pantoprazole Sodium | 68 | 21 |
| Famotidine | 50 | 22 |
| Esomeprazole Magnesium | 20 | — |
| Mesalamine | 13 | — |
Medicare Part D only. These counts cover prescriptions paid through Medicare Part D in 2024 — they do notinclude cash-pay, commercial-insurance, Medicaid, or Part B–administered drugs, and badly undercount high cash-pay categories (e.g. GLP-1 weight-loss, testosterone, and ED medications). Any drug with 10 or fewer claims is omitted by CMS, and beneficiary counts under 11 are suppressed — so a missing drug means no Part D record, never zero. This is a factual claims summary, not an endorsement, not medical advice, and not a consumer report. Source: CMS Medicare Part D Prescribers — by Provider and Drug.
Transparency — industry payments
Based on CMS Open Payments, 2024; not all care is captured.
$690 across 32 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
- 2005-11-15
- Last updated
- 2019-06-13
Frequently asked questions
- What is Mark Johnston's NPI number?
- Mark Johnston's National Provider Identifier (NPI) is 1003898131, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Johnston's specialty?
- Mark Johnston is listed in the NPPES registry with a primary specialty of Gastroenterology Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Johnston located?
- Mark Johnston's practice location on file with NPPES is 2112 Harrisburg Pike, Lancaster, PA 17601-2644.
- What is Mark Johnston's phone number?
- The practice phone number listed in the NPPES registry for Mark Johnston is (717) 544-3500.
- Does Mark Johnston accept Medicare?
- Mark Johnston is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Johnston's NPI active?
- Yes — Mark Johnston's NPI (1003898131) is active in the NPPES registry as of the last update on 2019-06-13.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.