Mark Johnson, M.D.
NPI 1861421372 · Gastroenterology Physician · Chula Vista, CA
Enrolled with Medicare as Practitioner - Gastroenterology · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Mark Johnson, M.D. is a Gastroenterology Physician provider in Chula Vista, CA (NPI 1861421372).
Provider details
- NPI number
- 1861421372
- Entity type
- Individual
- Primary specialty
- Gastroenterology PhysicianAllopathic & Osteopathic Physicians
- Credential
- M.D.
- Sex
- Male
- Sole proprietor
- No
- License
- G28163 (CA)
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
20 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
324 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) |
|---|---|---|
| Subsequent Hospital Care With Moderate Levelof Medical Decision Making, If Using Time, at Least 50 Minutes99233 | 215 | $120 |
| Initial Hospital Care With Moderate Level of Medical Decision Making, If Using Time, at Least 75 Minutes99223 | 59 | $175 |
| Biopsy of Esophagus, Stomach, And/Or Upper Small Bowel Using a Flexible Endoscope43239 | 26 | $113 |
| Diagnostic Exam of Large Bowel Using a Flexible Endoscope45378 | 12 | $185 |
| Established Patient Office Or Other Outpatient Visit With High Level of Medical Decision Making, If Using Time, 40 Minutes Or More99215 | 12 | $190 |
Typical Medicare-allowed amounts for these services range $113–$190 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
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 | 59 | 24 |
| Dicyclomine Hcl | 26 | 13 |
| Fluoxetine Hcl | 14 | — |
| Pantoprazole Sodium | 14 | — |
| Sodium Chloride/Nahco3/Kcl/Pegbrand: Peg 3350-Electrolyte | 12 | 12 |
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.
Practice location
Mailing address
Registry dates
- Enumerated
- 2006-06-30
- Last updated
- 2007-10-04
Frequently asked questions
- What is Mark Johnson's NPI number?
- Mark Johnson's National Provider Identifier (NPI) is 1861421372, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Mark Johnson's specialty?
- Mark Johnson is listed in the NPPES registry with a primary specialty of Gastroenterology Physician (Allopathic & Osteopathic Physicians).
- Where is Mark Johnson located?
- Mark Johnson's practice location on file with NPPES is 480 4th Ave, Chula Vista, CA 91910-4410.
- What is Mark Johnson's phone number?
- The practice phone number listed in the NPPES registry for Mark Johnson is (619) 585-0313.
- Does Mark Johnson accept Medicare?
- Mark Johnson is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Mark Johnson's NPI active?
- Yes — Mark Johnson's NPI (1861421372) is active in the NPPES registry as of the last update on 2007-10-04.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.