Quick answers
- Does Willem J. Van Der Werf accept Medicare assignment?
- Yes. Medicare's clinician data says Willem J. Van Der Werf 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 Willem J. Van Der Werf see?
- In 2024, CMS data shows 61 Original Medicare patients and 140 services for Willem J. Van Der Werf. This counts Original Medicare only and measures volume, not quality.
- What is Willem J. Van Der Werf's NPI number?
- 1275563397. 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 Willem J. Van Der Werf, 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 | 61 |
|---|---|
| Services billed to Medicare | 140 |
| Different services or procedures | 39 |
| Participating Medicare provider | Yes |
| Average age of these patients | 67 |
Most frequent services
- Subsequent hospital care with moderate levelof medical decision making, if using time, at least 35 minutes (99232)41 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%
- Chronic kidney disease56%
- Diabetes54%
- Arthritis30%
- Ischemic heart disease30%
Hospitals where Willem J. Van Der Werf works
Medicare's Facility Affiliation Data lists Willem J. Van Der Werf 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.
- Banner - University Medical Center PhoenixPhoenix, AZ · Acute Care Hospital · Medicare rating: 3 of 5 stars · Emergency services: listed by Medicare · CCN 030002
- St Josephs Hospital and Medical CenterPhoenix, AZ · Acute Care Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 030024
Practice locations
Addresses where Willem J. Van Der Werf is enrolled with Medicare (CMS data updated October 2, 2026).
- 2218 N 3rd StPhoenix, AZ 85004 (602) 252‑2543
- 350 W Thomas RdPhoenix, AZ 85013 (602) 406‑3000
Group practices
Medicare enrollment lists Willem J. Van Der Werf as a member of these groups (CMS data updated October 2, 2026).
- St. Joseph's Hospital and Medical Center21 clinicians in the group
- Arizona Transplant Associates PC5 clinicians in the group
Specialties
- General Surgeryprimary
Other general surgeons in Phoenix
Clinicians with the same Medicare primary specialty in Phoenix, AZ — not a recommendation.
Other clinicians in St. Joseph's Hospital and Medical Center
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | University Of California, San Francisco School Of Medicine |
| Graduation year | 1988 (38 years since medical school) |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1275563397 |
| 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