Quick answers
- Does William C. Leach Jr. accept Medicare assignment?
- Yes. Medicare's clinician data says William C. Leach Jr. accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of October 2, 2026. Ask the office to confirm before your visit.
- What is William C. Leach Jr.'s NPI number?
- 1558399279. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where William C. Leach Jr. works
Medicare's Facility Affiliation Data lists William C. Leach Jr. at these hospitals (updated October 2, 2026). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians. Star rating and emergency services: Hospital General Information (CMS), data updated October 26, 2026.
- Mercy Health System CorpJanesville, WI · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 520066
- Mercy Walworth Hospital & Medical CenterLake Geneva, WI · Critical Access Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 521357
Practice locations
Addresses where William C. Leach Jr. is enrolled with Medicare (CMS data updated October 2, 2026).
- 875 S Route 31Crystal Lake, IL 60014 (779) 220‑5500
- N2950 State Rd, Suite 67Lake Geneva, WI 53147 (262) 245‑0535
Group practices
Medicare enrollment lists William C. Leach Jr. as a member of this group (CMS data updated October 2, 2026).
- Mercy Health System Corporation753 clinicians in the group
Specialties
- Obstetrics/Gynecologyprimary
Other OB-GYNs in Illinois
Clinicians with the same Medicare primary specialty in Illinois — not a recommendation.
Other clinicians in Mercy Health System Corporation
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Graduation year | 2002 (24 years since medical school) |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1558399279 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated October 2, 2026, retrieved October 29, 2026
- Hospital General Information — CMS, data updated October 26, 2026, retrieved November 13, 2026
- National Downloadable File (Doctors and Clinicians) — CMS, data updated October 2, 2026, retrieved October 29, 2026
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians