Quick answers
- Which hospitals does William Grehan work at?
- Medicare's official clinician data lists William Grehan at 5 hospitals: Advocate Christ Hospital & Medical Center, Black Hills Surgical Hospital LLC, Coastal Carolina Hospital, Memorial Hospital and Novant Health Hilton Head Medical Center. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does William Grehan see patients?
- Medicare's clinician data lists 5 practice locations, including Shiloh, IL, Rapid City, SD and Hilton Head, SC. Call before your visit to confirm the address.
- What is William Grehan's specialty?
- Medicare lists Anesthesiology as the primary specialty.
- Does William Grehan accept Medicare assignment?
- Yes. Medicare's clinician data says William Grehan 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 Grehan?
- (618) 607-1000, as listed in official Medicare / NPI Registry data.
- What is William Grehan's NPI number?
- 1417961061. 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 Grehan works
Medicare's Facility Affiliation Data lists William Grehan at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- Advocate Christ Hospital & Medical CenterOak Lawn, IL · Acute Care Hospital · CCN 140208
- Black Hills Surgical Hospital LLCRapid City, SD · Acute Care Hospital · CCN 430091
- Coastal Carolina HospitalHardeeville, SC · Acute Care Hospital · CCN 420101
- Memorial HospitalBelleville, IL · Acute Care Hospital · CCN 140185
- Novant Health Hilton Head Medical CenterHilton Head Island, SC · Acute Care Hospital · CCN 420080
Practice locations
Addresses where William Grehan is enrolled with Medicare (CMS data updated 2026-10-02).
- 1404 Cross StShiloh, IL 62269 (618) 607‑1000
- 216 Anamaria DrRapid City, SD 57701 (605) 721‑4700
- 25 Hospital Ctr BlvdHilton Head, SC 29926 (843) 681‑6122
- 4440 W 95th StOak Lawn, IL 60453 (708) 684‑4393
- 4500 Memorial DrBelleville, IL 62226 (618) 233‑7750
Group practices
Medicare enrollment lists William Grehan as a member of these groups (CMS data updated 2026-10-02).
- Advocate Health and Hospitals Corporation3,118 clinicians in the group
- Cep America - Anesthesia PC849 clinicians in the group
- Midwest Anesthesia Providers SC182 clinicians in the group
- Black Hills Surgical Hospital LLC174 clinicians in the group
Specialties
- Anesthesiologyprimary
Other anesthesiologists in Shiloh
Clinicians with the same Medicare primary specialty in Shiloh, IL — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Graduation year | 1988 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1417961061 |
| 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