Mark Janczewski, MD, MPH
Mark Janczewski, MD, MPH is a Clinical Informatics Physician in Alexandria, VA, registered under NPI 1124022843. This provider registers 4 separate taxonomy codes, which usually means they practise across more than one recognised specialty. NPPES records them as a sole proprietor, meaning the practice is not incorporated as a separate legal entity.
Getting there
The practice address on file is 425 S PAYNE ST, Alexandria, VA 22314. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| 0101041106 | VA | Clinical Informatics Physician primary |
| 0101041106 | VA | Preventive Medicine/Occupational… |
| 0101041106 | VA | Family Medicine Physician |
| 0101041106 | VA | Aerospace Medicine Physician |
This provider holds licence 0101041106 issued in VA. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
This NPI does not appear in the PECOS Medicare enrolment file. Providers who do not bill Medicare — or who bill only through a group's enrolment — will not appear here. It is not a sign of any problem with the registration.
What Clinical Informatics covers
Physicians who practice Clinical Informatics collaborate with other health care and information technology professionals to analyze, design, implement and evaluate information and communication systems that enhance individual and population health outcomes, improve patient care, and strengthen the clinician-patient relationship. Clinical Informaticians use their knowledge of patient care combined with their understanding of informatics concepts, methods, and tools to: assess information and knowledge needs of health care professionals and patients; characterize, evaluate, and refine clinical processes; develop, implement, and refine clinical decision support systems; and lead or participate in the procurement, customization, development, implementation, management, evaluation, and continuous improvement of clinical information systems. NUCC Health Care Provider Taxonomy, code 2083C0008X
All registered taxonomy codes
This provider registers 4 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 2083C0008X | Clinical Informatics Physician Clinical Informatics | 0101041106 | VA | primary |
| 2083P0500X | Preventive Medicine/Occupational Environmental Medicine Physician Preventive Medicine/Occupational Environmental Medicine | 0101041106 | VA | |
| 207Q00000X | Family Medicine Physician | 0101041106 | VA | |
| 2083A0100X | Aerospace Medicine Physician Aerospace Medicine | 0101041106 | VA |
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1124022843 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Jun 9, 2005 |
| Last updated | Sep 3, 2025 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | MD, MPH |
| Practice address |
425 S PAYNE ST Alexandria, VA 22314 (703) 994-7637 |
| Other identifiers |
0101041106
· LICENSE (VA) ME175967 · LICENSE (FL) |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 1 | 2 | 4 | 0 | 2 | 2 | 8 | 4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 1 | 4 | 4 | 0 | 2 | 4 | 8 | 8 |
Sum = 57 · next multiple of 10 = 60 · check digit = 3 · actual last digit = 3
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.