Jonathan Lo, MD
Internal Medicine Physician · Fontana, CA
Jonathan Lo, MD is an internal medicine physician with a practice address in Fontana, California, and NPI 1164570941, issued on Jan 8, 2007. Check the license (California A66923, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Jonathan Lo
- Credential
- MD
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- A66923 CA
Self-reported in NPPES; status is on the state search - Practice location
- 9961 Sierra Ave, Fontana, CA 92335
- Phone
- (909) 427-3910
- Enumerated
- Jan 8, 2007
- Record last updated
- Dec 2, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicare enrollment
- Enrolled (PECOS I20081120000790); accepts Medicare assignment
- Medical or professional school
- Un Of California, Irvine, College Of Medicine, 1997
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 9961 Sierra Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Jonathan Lo in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A66923Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
86% fewer Medicare Part D claims than the average internal medicine physician in 2024
438 Medicare Part D claims for 168 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Most prescribed
- Furosemide26 claims
- Cefpodoxime Proxetil25 claims
- Pantoprazole Sodium23 claims
- Atorvastatin Calcium20 claims
- Potassium Chloride20 claims
- Clopidogrel17 claims
Source: CMS Medicare Part D Prescribers by Provider and Drug, 2024 (data.cms.gov). Part D covers prescriptions for Medicare patients only; drugs with fewer than 11 claims are not published.
Bills Medicare through one group practice
- Southern California Permanente Medical GroupFontana, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Jonathan Lo among 17,696 internal medicine physician records in California
Jonathan Lo, MD is one of 17,696 internal medicine physician records with a practice address in California. 79% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2007, is newer than 44% of them.
- NPI issued2007 · 44% of these records are older, 44% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated1997 · median 2004 among the 11,065 with a school on file
- Record last updated2021 · 61% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207R00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
111 internal medicine physician records list a practice address in Fontana
They are 111 of the 3,012 NPPES records with a practice address in Fontana, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Fontana → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Te-Ie Lee, M.D.Fontana, CA 923351982613931
- Hollis Lee, MDFontana, CA 923351588736060
- Hoveda Mufti, M.D.Fontana, CA 923351598871493
- J Duc Nguyen, M.D.Fontana, CA 923351427018456
- Joseph Paredes, MDFontana, CA 923351457422420
- Ramesh Patel, MDFontana, CA 923351750480810
- Alex Quan, MDFontana, CA 923351659442630
- Gregory Shimizu, MDFontana, CA 923351154492130
Common questions
What is Jonathan Lo, MD's NPI number?
Jonathan Lo, MD's National Provider Identifier (NPI) is 1164570941, issued on Jan 8, 2007. An NPI identifies a provider in billing; it is not a license.
Where is Jonathan Lo, MD located?
The NPPES record lists a practice address at 9961 Sierra Ave, Fontana, CA, 92335. Phone: (909) 427-3910. Providers update this record themselves, so call before visiting.
How can I verify Jonathan Lo, MD's license?
NPPES lists California license number A66923, as entered by the provider. Search the Medical Board of California at https://www.mbc.ca.gov/License-Verification/default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
How much does Jonathan Lo, MD prescribe under Medicare Part D?
In 2024, Jonathan Lo, MD had 438 Medicare Part D claims for 168 beneficiaries; the average among internal medicine physician prescribers was 3,176. Part D covers Medicare prescriptions only.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. Medicare files from data.cms.gov. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.