Quick answers
- Does William T. Larsen accept Medicare assignment?
- Yes. Medicare's clinician data says William T. Larsen 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.
- How many Medicare patients does William T. Larsen see?
- In 2024, CMS data shows 83 Original Medicare patients and 133 services for William T. Larsen. This counts Original Medicare only and measures volume, not quality.
- What is William T. Larsen's NPI number?
- 1356711584. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Medicare activity in 2024
Official CMS public-use data for William T. Larsen, data year 2024 (released May 21, 2026). It covers Original Medicare (fee-for-service) patients only, not Medicare Advantage or other insurance. It shows volume, not quality or outcomes. CMS hides any count of 10 or fewer patients.
| Original Medicare patients | 83 |
|---|---|
| Services billed to Medicare | 133 |
| Different services or procedures | 5 |
| Participating Medicare provider | Yes |
| Average age of these patients | 77 |
Most frequent services
- Subsequent hospital care with moderate levelof medical decision making, if using time, at least 35 minutes (99232)100 services
- Initial hospital care with straightforward or low level of medical decision making, per day, if using time, at least 40 minutes (99221)18 services
- Initial hospital care with straightforward or low-level medical decision making, if using time, at least 55 minutes (99222)12 services
Chronic conditions among these patients
Share of this clinician’s Original Medicare patients with each condition, as published by CMS (it describes the patients, not the care given).
- High blood pressure75%
- High cholesterol75%
- Arthritis71%
- Stroke or mini-stroke59%
- Ischemic heart disease52%
- Chronic kidney disease48%
Hospitals where William T. Larsen works
Medicare's Facility Affiliation Data lists William T. Larsen 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.
- Alexian Brothers Medical Center 1Elk Grove Village, IL · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 140258
- Presence Mercy Medical CenterAurora, IL · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 140174
- Saint Joseph Medical CenterJoliet, IL · Acute Care Hospital · Medicare rating: 1 of 5 stars · Emergency services: listed by Medicare · CCN 140007
- St Alexius Medical CenterHoffman Estates, IL · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: listed by Medicare · CCN 140290
- The University of Chicago Medical CenterChicago, IL · Acute Care Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 140088
Practice locations
Addresses where William T. Larsen is enrolled with Medicare (CMS data updated October 2, 2026).
- 1555 Barrington RdHoffman Estates, IL 60169
- 1786 Moon Lake BlvdHoffman Est, IL 60194 (847) 755‑8208
- 5841 S Maryland AveChicago, IL 60637 (888) 824‑0200
- 800 Biesterfield RdElk Grove Village, IL 60007
Group practices
Medicare enrollment lists William T. Larsen as a member of these groups (CMS data updated October 2, 2026).
- University of Chicago1,712 clinicians in the group
- Bonaventure Medical Foundation LLC167 clinicians in the group
Specialties
- Physician Assistantprimary
Other physician assistants in Hoffman Estates
Clinicians with the same Medicare primary specialty in Hoffman Estates, IL — not a recommendation.
Other clinicians in University of Chicago
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Graduation year | 2015 |
|---|---|
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1356711584 |
| 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
- Medicare Physician & Other Practitioners - by Provider — CMS, data year 2024, released May 21, 2026; Medicare Physician & Other Practitioners - by Provider and Service
- 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