Quick answers
- Does Timothy R. Wassenaar accept Medicare assignment?
- Yes. Medicare's clinician data says Timothy R. Wassenaar 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 Timothy R. Wassenaar see?
- In 2024, CMS data shows 332 Original Medicare patients and 644 services for Timothy R. Wassenaar. This counts Original Medicare only and measures volume, not quality.
- What is Timothy R. Wassenaar's NPI number?
- 1518928993. 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 Timothy R. Wassenaar, 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 | 332 |
|---|---|
| Services billed to Medicare | 644 |
| Different services or procedures | 14 |
| Participating Medicare provider | Yes |
| Average age of these patients | 76 |
Most frequent services
- Established patient office or other outpatient visit with moderate level of decision making, if using time, 30 minutes or more (99214)223 services
- Established patient office or other outpatient visit with high level of medical decision making, if using time, 40 minutes or more (99215)152 services
- Subsequent hospital care with moderate levelof medical decision making, if using time, at least 35 minutes (99232)81 services
- Subsequent hospital care with moderate levelof medical decision making, if using time, at least 50 minutes (99233)63 services
- New patient office or other outpatient visit with a high level of medical decision making, if using time, 60 minutes or more (99205)53 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%
- Arthritis59%
- Chronic kidney disease40%
- Ischemic heart disease38%
- Atrial fibrillation28%
Hospitals where Timothy R. Wassenaar works
Medicare's Facility Affiliation Data lists Timothy R. Wassenaar 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.
- Oconomowoc Memorial HospitalOconomowoc, WI · Acute Care Hospital · Medicare rating: 5 of 5 stars · Emergency services: listed by Medicare · CCN 520062
- Waukesha Memorial HospitalWaukesha, WI · Acute Care Hospital · Medicare rating: 4 of 5 stars · Emergency services: listed by Medicare · CCN 520008
Practice locations
Addresses where Timothy R. Wassenaar is enrolled with Medicare (CMS data updated October 2, 2026). The first 5 of 7; the Medicare profile lists all.
- 18905 W Capitol Dr, Suite 110Brookfield, WI 53045 (866) 432‑7855
- 725 American AveWaukesha, WI 53188
- 791 Summit AveOconomowoc, WI 53066
- N14W24100 Riverwood DrWaukesha, WI 53188
- N16W24131 Riverwood DrWaukesha, WI 53188 (262) 696‑0808
Group practices
Medicare enrollment lists Timothy R. Wassenaar as a member of this group (CMS data updated October 2, 2026).
- Prohealth Medical Group Inc479 clinicians in the group
Specialties
- Hematology/Oncologyprimary
Other hematologist-oncologists in Wisconsin
Clinicians with the same Medicare primary specialty in Wisconsin — not a recommendation.
Other clinicians in Prohealth Medical Group Inc
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) |
| Telehealth | Offers telehealth services |
| NPI (National Provider Identifier) | 1518928993 |
| 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