Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum
Mary E Wassilak, WHNP-BC
Nurse Practitioner in Geneva, IL · enumerated 2009.
Data current as of Jul 13, 2026 · sourced from CMS NPPES
National Provider Identifier
1811138944
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Registry record
Entity type Individual (Type 1)
Name Mary E Wassilak
Credential WHNP-BC
Sex Female
Practice address 351 Delnor Dr Ste 204, Geneva, IL, 60134
Phone (630) 208-0784
Fax (630) 938-9190
Enumeration date Mar 19, 2009
Last updated in NPPES Oct 6, 2023
Taxonomy & licenses
363LW0102X Women's Health Nurse Practitioner Physician Assistants & Advanced Practice Nursing Providers · License 209.006774 (IL) Secondary
363LX0001X Obstetrics & Gynecology Nurse Practitioner Physician Assistants & Advanced Practice Nursing Providers · License 209006774 (IL) Secondary
363L00000X Nurse Practitioner Physician Assistants & Advanced Practice Nursing Providers · License 209006774 (IL) Primary
What is an NPI number?
A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.
Frequently asked questions
What specialty is Mary Wassilak?
Mary Wassilak is registered in NPPES with the primary taxonomy of Nurse Practitioner. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.
Is this the official NPI registry?
No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.
Other providers at this practice address
Browse all →Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2023-10-06.