Justin Chau, M.D.
Justin Chau, M.D. is a Hematology & Oncology Physician in Grafton, WI, registered under NPI 1871974154. 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 975 PORT WASHINGTON RD, Grafton, WI 53024. 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 |
|---|---|---|
| MD-45076 | IA | Medical Oncology Physician |
| MD-45076 | IA | Hematology & Oncology Physician |
| 82045 | WI | Hematology & Oncology Physician primary |
| MD-45076 | IA | Internal Medicine Physician |
Licences are recorded in 2 states: IA, WI. Providers licensed in several states often practise near a state border or deliver telehealth across state lines.
- Status
- Approved
- Provider type
- Practitioner - Hematology/oncology
- PAC ID
- 3870805666
- Enrollment ID
- I20230522000534
Medicare enrolment is recorded as approved under the provider type Practitioner - Hematology/oncology. 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.
Licensed in 2 states
This provider holds licences in 2 states: Iowa and Wisconsin. The practice address on file is in Grafton, WI, but a licence in another state usually means they see patients there too — either at a second location or by telehealth. If the address above is far from you, it is worth calling to ask whether they practise closer to where you live.
- Licence
- 82045
- Specialty
- Hematology & Oncology Physician
Licence numbers are self-reported to NPPES at registration. They do not confirm a licence is currently active, in good standing, or valid for the specialty shown — only the state board can tell you that, which is why we link to each one.
What Hematology & Oncology covers
An internist doctor of osteopathy that specializes in the treatment of the combination of hematology and oncology disorders. A doctor of osteopathy that is board eligible/certified by the American Osteopathic Board of Internal Medicine WAS able to obtain a Certificate of Special Qualifications in the field of Hematology and Oncology. The Certificate is NO longer offered. NUCC Health Care Provider Taxonomy, code 207RH0003X
All registered taxonomy codes
This provider registers 4 taxonomy codes. The primary code is what appears on most claims; the others record additional recognised specialties.
| Code | Specialty | Licence | State | |
|---|---|---|---|---|
| 207RX0202X | Medical Oncology Physician Medical Oncology | MD-45076 | IA | |
| 207RH0003X | Hematology & Oncology Physician Hematology & Oncology | MD-45076 | IA | |
| 207RH0003X | Hematology & Oncology Physician Hematology & Oncology | 82045 | WI | primary |
| 207R00000X | Internal Medicine Physician | MD-45076 | IA |
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 | 1871974154 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Jun 12, 2015 |
| Last updated | May 5, 2026 |
| Status | Active |
| Sole proprietor | No |
| Gender | Male |
| Credential | M.D. |
| Practice address |
975 PORT WASHINGTON RD Grafton, WI 53024 |
| Mailing address |
PO BOX 735044 Chicago, IL 60673 |
| Other identifiers |
100236288
· Medicaid (WI) |
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 | 8 | 7 | 1 | 9 | 7 | 4 | 1 | 5 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 8 | 5 | 1 | 9 | 7 | 8 | 1 | 1 |
Sum = 66 · next multiple of 10 = 70 · check digit = 4 · actual last digit = 4
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.