Gary Altwerger, M.D.
Gary Altwerger, M.D. is a Gynecologic Oncology Physician in Chicago, IL, registered under NPI 1407114630. NPPES records them as a sole proprietor, meaning the practice is not incorporated as a separate legal entity.
Getting there
The practice address on file is 5841 S MARYLAND AVE, Chicago, IL 60637. We have not yet mapped what surrounds this office — parking, transit, and nearby pharmacies are added as our data collection reaches each location.
Credentials and Medicare
| Licence | State | Specialty |
|---|---|---|
| 036176993 | IL | Gynecologic Oncology Physician primary |
This provider holds licence 036176993 issued in IL. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
- Status
- Approved
- Provider type
- Practitioner - Obstetrics/gynecology
- PAC ID
- 2466769849
Enrolled in Medicare 2 times, across 2 states:
| State | Enrollment ID | Provider type |
|---|---|---|
| Connecticut | I20160805001059 | Practitioner - Obstetrics/gynecology |
| Illinois | I20251105003308 | Practitioner - Gynecological Oncology |
Medicare enrolment is recorded as approved under the provider type Practitioner - Obstetrics/gynecology. There are 2 separate enrolment records across 2 states (CT, IL). Multiple enrolments usually mean the provider bills Medicare from more than one practice location, or has kept an earlier enrolment after moving. Each record carries its own enrolment ID, listed above. Being enrolled means the provider can bill Medicare; it does not tell you whether they are currently accepting new Medicare patients. Call the office to confirm.
What Gynecologic Oncology covers
An obstetrician/gynecologist who provides consultation and comprehensive management of patients with gynecologic cancer, including those diagnostic and therapeutic procedures necessary for the total care of the patient with gynecologic cancer and resulting complications. NUCC Health Care Provider Taxonomy, code 207VX0201X
The taxonomy records how the provider classifies their own practice. It does not confirm which conditions they currently treat, whether they are accepting new patients, or which insurance they take — call the office for that.
Full NPPES record
An NPI-1 identifies a single person. It stays with the clinician for life, even if they move practice or change state, which is why the address on file can lag behind where they actually work today.
| NPI | 1407114630 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Apr 25, 2012 |
| Last updated | Jan 15, 2026 |
| Status | Active |
| Sole proprietor | Yes |
| Credential | M.D. |
| Practice address |
5841 S MARYLAND AVE Chicago, IL 60637 (888) 824-0200 |
| Mailing address |
150 HARVESTER DR STE 300 Burr Ridge, IL 60527 |
Number check
How the check works, step by step
Every NPI carries a Luhn check digit — the same scheme used on credit cards. CMS prefixes the number with 80840 before computing it, which marks it as a US health identifier.
| Digit | 8 | 0 | 8 | 4 | 0 | 1 | 4 | 0 | 7 | 1 | 1 | 4 | 6 | 3 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 4 | 0 | 7 | 2 | 1 | 8 | 6 | 6 |
Sum = 60 · next multiple of 10 = 60 · check digit = 0 · actual last digit = 0
A valid check digit only means the number is well-formed. It does not mean the provider is licensed, active, or in good standing — those are separate questions answered by the sections above.