John Ong, DO
John Ong, DO is a Nephrology Physician in Fountain Valley, CA, registered under NPI 1477056406.
Getting there
The practice address on file is 11100 WARNER AVE STE 218, Fountain Valley, CA 92708. 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 |
|---|---|---|
| 20A21125 | CA | Nephrology Physician primary |
This provider holds licence 20A21125 issued in CA. 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 - Nephrology
- PAC ID
- 9638593916
Medicare enrolment is recorded as approved under the provider type Practitioner - Nephrology. This means the provider is enrolled to bill Medicare, though it does not tell you whether they are currently accepting new Medicare patients. Call the office to confirm.
What Nephrology covers
An internist who treats disorders of the kidney, high blood pressure, fluid and mineral balance and dialysis of body wastes when the kidneys do not function. This specialist consults with surgeons about kidney transplantation. NUCC Health Care Provider Taxonomy, code 207RN0300X
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 | 1477056406 valid check digit |
|---|---|
| Entity type | Individual (NPI-1) |
| Enumeration date | Mar 15, 2018 |
| Last updated | Jan 16, 2026 |
| Status | Active |
| Sole proprietor | No |
| Credential | DO |
| Practice address |
11100 WARNER AVE STE 218 Fountain Valley, CA 92708 (714) 641-9696 Fax (714) 641-1211 |
| Mailing address |
9373 HAZARD WAY STE 200 San Diego, CA 92123 |
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 | 7 | 7 | 0 | 5 | 6 | 4 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubled? | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 | — | ×2 |
| Value | 8 | 0 | 8 | 8 | 0 | 2 | 4 | 5 | 7 | 0 | 5 | 3 | 4 | 0 |
Sum = 54 · next multiple of 10 = 60 · check digit = 6 · actual last digit = 6
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.