Sydney Mesker
Sydney Mesker is a Professional Counselor in Oak Park, IL, registered under NPI 1871454090.
Getting there
The practice address on file is 1010 LAKE ST STE 500, Oak Park, IL 60301. 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 |
|---|---|---|
| 178.021993 | IL | Professional Counselor primary |
This provider holds licence 178.021993 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 | 1871454090 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Nov 18, 2025 |
| Last updated | Nov 18, 2025 |
| Status | Active |
| Sole proprietor | No |
| Gender | Female |
| Practice address |
1010 LAKE ST STE 500 Oak Park, IL 60301 (773) 665-8052 |
| Mailing address |
10101 S PEORIA ST Chicago, IL 60643 |
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 | 8 | 7 | 1 | 4 | 5 | 4 | 0 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 8 | 5 | 1 | 8 | 5 | 8 | 0 | 9 |
Sum = 70 · next multiple of 10 = 70 · check digit = 0 · actual last digit = 0
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.