Gillian Thornhill, L.P.C.
Gillian Thornhill, L.P.C. is a Professional Counselor in Park Ridge, IL, registered under NPI 1407975949. 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 422 N NORTHWEST HWY STE 335, Park Ridge, IL 60068. 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 |
|---|---|---|
| 178003972 | IL | Professional Counselor primary |
This provider holds licence 178003972 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 Professional covers
Definition to come... NUCC Health Care Provider Taxonomy, code 101YP2500X
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 | 1407975949 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Mar 28, 2007 |
| Last updated | May 12, 2026 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | L.P.C. |
| Practice address |
422 N NORTHWEST HWY STE 335 Park Ridge, IL 60068 (847) 894-6442 Fax (630) 954-6066 |
| Mailing address |
422 N NORTHWEST HWY STE B4 Park Ridge, IL 60068 |
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 | 4 | 0 | 7 | 9 | 7 | 5 | 9 | 4 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 4 | 0 | 7 | 9 | 7 | 1 | 9 | 8 |
Sum = 71 · next multiple of 10 = 80 · 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.