Ellen Zemarkowitz, LCSW
Ellen Zemarkowitz, LCSW is a Mental Health Counselor in Palo Alto, CA, registered under NPI 1053252957. This provider registers 2 separate taxonomy codes, which usually means they practise across more than one recognised specialty.
Getting there
The practice address on file is 725 WELCH RD, Palo Alto, CA 94304. 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 |
|---|---|---|
| LCSW89459 | CA | Clinical Social Worker |
| 89459 | CA | Mental Health Counselor primary |
This provider holds licence LCSW89459 issued in CA. 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 Mental Health covers
Definition to come... NUCC Health Care Provider Taxonomy, code 101YM0800X
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 | |
|---|---|---|---|---|
| 1041C0700X | Clinical Social Worker Clinical | LCSW89459 | CA | |
| 101YM0800X | Mental Health Counselor Mental Health | 89459 | CA | primary |
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 | 1053252957 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Apr 3, 2026 |
| Last updated | Jul 30, 2026 |
| Status | Active |
| Sole proprietor | No |
| Gender | Female |
| Credential | LCSW |
| Practice address |
725 WELCH RD Palo Alto, CA 94304 (650) 497-8000 |
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 | 5 | 3 | 2 | 5 | 2 | 9 | 5 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 0 | 1 | 3 | 4 | 5 | 4 | 9 | 1 |
Sum = 53 · next multiple of 10 = 60 · check digit = 7 · actual last digit = 7
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.