Quick answers
- Which hospitals does William Tillis work at?
- Medicare's official clinician data lists William Tillis at 2 hospitals: Mercy Health System Corp and Mercy Walworth Hospital & Medical Center. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does William Tillis see patients?
- Medicare's clinician data lists 3 practice locations, including Janesville, WI, Crystal Lake, IL and Lake Geneva, WI. Call before your visit to confirm the address.
- What is William Tillis's specialty?
- Medicare lists Pulmonary Disease as the primary specialty, and also Internal Medicine.
- Does William Tillis accept Medicare assignment?
- Yes. Medicare's clinician data says William Tillis accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for William Tillis?
- (608) 756-6000, as listed in official Medicare / NPI Registry data.
- What is William Tillis's NPI number?
- 1669468377. 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 Tillis works
Medicare's Facility Affiliation Data lists William Tillis at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- Mercy Health System CorpJanesville, WI · Acute Care Hospital · CCN 520066
- Mercy Walworth Hospital & Medical CenterLake Geneva, WI · Critical Access Hospital · CCN 521357
Practice locations
Addresses where William Tillis is enrolled with Medicare (CMS data updated 2026-10-02).
- 1000 Mineral Point AveJanesville, WI 53548 (608) 756‑6000
- 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 Tillis as a member of this group (CMS data updated 2026-10-02).
- Mercy Health System Corporation753 clinicians in the group
Specialties
- Pulmonary Diseaseprimary
- Internal Medicinealso
Other pulmonologists in Janesville
Clinicians with the same Medicare primary specialty in Janesville, WI — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | University Of Illinois College Of Med (chi/peor/rock/chm-Urb) |
| Graduation year | 1986 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1669468377 |
| 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 2026-10-02, retrieved 2026-10-29
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- 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