Gerard Cerniak, M.D.
Gerard Cerniak, M.D. is a Gastroenterology Physician in Joliet, IL, registered under NPI 1003587049. This provider registers 2 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 208 TIMBERLINE CT., Joliet, IL 60431. 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 |
|---|---|---|
| 36-46439 | IL | Gastroenterology Physician primary |
| 36-46439 | IL | Internal Medicine Physician |
This provider holds licence 36-46439 issued in IL. 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 Gastroenterology covers
An internist who specializes in diagnosis and treatment of diseases of the digestive organs including the stomach, bowels, liver and gallbladder. This specialist treats conditions such as abdominal pain, ulcers, diarrhea, cancer and jaundice and performs complex diagnostic and therapeutic procedures using endoscopes to visualize internal organs. NUCC Health Care Provider Taxonomy, code 207RG0100X
All registered taxonomy codes
This provider registers 2 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 207RG0100X | Gastroenterology Physician Gastroenterology | 36-46439 | IL | primary |
| 207R00000X | Internal Medicine Physician | 36-46439 | IL |
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 | 1003587049 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Sep 21, 2021 |
| Last updated | Dec 15, 2021 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | M.D. |
| Practice address |
208 TIMBERLINE CT. Joliet, IL 60431 (815) 744-7507 |
| Mailing address |
208 TIMBERLINE CT Joliet, IL 60431 |
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 | 0 | 0 | 3 | 5 | 8 | 7 | 0 | 4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 0 | 0 | 3 | 1 | 8 | 5 | 0 | 8 |
Sum = 51 · next multiple of 10 = 60 · check digit = 9 · actual last digit = 9
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.