William Marrero-leon, M.D
William Marrero-leon, M.D is a Medical Oncology Physician in Houston, TX, registered under NPI 1336688274. 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 1515 HOLCOMBE BLVD, Houston, TX 77030. 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 |
|---|---|---|
| V7258 | TX | Medical Oncology Physician primary |
| V7258 | TX | Hematology (Internal Medicine) Physician |
| V7258 | TX | Internal Medicine Physician |
This provider holds licence V7258 issued in TX. A licence number in NPPES reflects what was filed at registration — it does not confirm the licence is still active today.
This NPI does not appear in the PECOS Medicare enrolment file. Providers who do not bill Medicare — or who bill only through a group's enrolment — will not appear here. It is not a sign of any problem with the registration.
What Medical Oncology covers
An internist who specializes in the diagnosis and treatment of all types of cancer and other benign and malignant tumors. This specialist decides on and administers therapy for these malignancies as well as consults with surgeons and radiotherapists on other treatments for cancer. NUCC Health Care Provider Taxonomy, code 207RX0202X
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 | |
|---|---|---|---|---|
| 207RX0202X | Medical Oncology Physician Medical Oncology | V7258 | TX | primary |
| 207RH0000X | Hematology (Internal Medicine) Physician Hematology | V7258 | TX | |
| 207R00000X | Internal Medicine Physician | V7258 | TX |
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 | 1336688274 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Feb 13, 2017 |
| Last updated | Apr 14, 2026 |
| Status | Active |
| Sole proprietor | No |
| Credential | M.D |
| Practice address |
1515 HOLCOMBE BLVD Houston, TX 77030 (713) 792-6161 |
| Mailing address |
PO BOX 4439 Houston, TX 77210 |
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 | 3 | 3 | 6 | 6 | 8 | 8 | 2 | 7 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 3 | 6 | 6 | 3 | 8 | 7 | 2 | 5 |
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.