Christopher Greb, MD
Christopher Greb, MD is an Allergy & Immunology (Internal Medicine) Physician in Chicago, IL, registered under NPI 1134623895. This provider registers 3 separate taxonomy codes, which usually means they practise across more than one recognised specialty.
Getting there
The practice address on file is 1725 W HARRISON STREET STE 970, Chicago, IL 60612. 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 |
|---|---|---|
| 125.075689 | IL | Internal Medicine Physician |
| 036165118 | IL | Allergy & Immunology (Internal Medicine)… primary |
This provider holds licence 125.075689 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 - Allergy/immunology
- PAC ID
- 3375953011
- Enrollment ID
- I20250905003609
Medicare enrolment is recorded as approved under the provider type Practitioner - Allergy/immunology. 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 Allergy & Immunology covers
An internist doctor of osteopathy that specializes in the treatment of allergy and immunologic disorders. A doctor of osteopathy that is board eligible/certified by the American Osteopathic Board of Internal Medicine can obtain a Certificate of Special Qualifications in the field of Allergy & Immunology. NUCC Health Care Provider Taxonomy, code 207RA0201X
All registered taxonomy codes
This provider registers 3 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 207R00000X | Internal Medicine Physician | 125.075689 | IL | |
| 390200000X | Student in an Organized Health Care Education/Training Program | — | — | |
| 207RA0201X | Allergy & Immunology (Internal Medicine) Physician Allergy & Immunology | 036165118 | IL | primary |
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 | 1134623895 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Mar 19, 2018 |
| Last updated | Jun 26, 2023 |
| Status | Active |
| Sole proprietor | No |
| Gender | Male |
| Credential | MD |
| Practice address |
1725 W HARRISON STREET STE 970 Chicago, IL 60612 (312) 942-6979 |
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 | 1 | 3 | 4 | 6 | 2 | 3 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 1 | 6 | 4 | 3 | 2 | 6 | 8 | 9 |
Sum = 65 · next multiple of 10 = 70 · check digit = 5 · actual last digit = 5
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.