Quick answers
- Does Gregory S. Retzinger accept Medicare assignment?
- Yes. Medicare's clinician data says Gregory S. Retzinger 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 Gregory S. Retzinger see?
- In 2024, CMS data shows 919 Original Medicare patients and 10,479 services for Gregory S. Retzinger. This counts Original Medicare only and measures volume, not quality.
- What is Gregory S. Retzinger's NPI number?
- 1053334755. 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 Gregory S. Retzinger, 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 | 919 |
|---|---|
| Services billed to Medicare | 10,479 |
| Different services or procedures | 19 |
| Participating Medicare provider | Yes |
| Average age of these patients | 74 |
Most frequent services
- Complete blood cell count (red cells, white blood cell, platelets), automated test and automated differential white blood cell count (85025)4,514 services
- Blood test, comprehensive group of blood chemicals (80053)3,948 services
- Lactate dehydrogenase (enzyme) level (83615)705 services
- Magnesium level (83735)490 services
- Uric acid level, blood (84550)248 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%
- Arthritis47%
- Cancer (breast, colorectal, lung, prostate, endometrial or leukemia/lymphoma)47%
- Ischemic heart disease35%
- Diabetes32%
Practice locations
Addresses where Gregory S. Retzinger is enrolled with Medicare (CMS data updated October 2, 2026).
Group practices
Medicare enrollment lists Gregory S. Retzinger as a member of this group (CMS data updated October 2, 2026).
- Northwestern Medical Faculty Foundation4,503 clinicians in the group
Specialties
- Pathologyprimary
Other pathologists in Illinois
Clinicians with the same Medicare primary specialty in Illinois — not a recommendation.
Other clinicians in Northwestern Medical Faculty Foundation
Medicare enrollment lists these clinicians in the same group practice — not a recommendation.
Clinician information
| Medical school | University Of Chicago, Pritzker School Of Medicine |
|---|---|
| Graduation year | 1983 (43 years since medical school) |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1053334755 |
| 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
- 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