Karthikeyan Viswanathan, DO
Internal Medicine Physician · Los Altos, CA
Karthikeyan Viswanathan, DO is an internal medicine physician with a practice address in Los Altos, California, and NPI 1396128336, issued on Jul 8, 2015. Check the license (California 20A19044, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Karthikeyan Viswanathan
- Credential
- DO
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 20A19044 CA
Self-reported in NPPES; status is on the state search - Practice location
- 4546 EL Camino Real Ste B7, Los Altos, CA 94022
- Phone
- (866) 362-4246
- Enumerated
- Jul 8, 2015
- Record last updated
- Aug 21, 2025
- Fax
- (650) 260-6030
- Medicare enrollment
- Enrolled (PECOS I20250116000720); may accept Medicare assignment
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Also registered at 4546 EL Camino Real Ste B7
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Karthikeyan Viswanathan in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A19044Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
88% fewer Medicare Part D claims than the average internal medicine physician in 2024
389 Medicare Part D claims for 56 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Most prescribed
- Lisinopril44 claims
- Atorvastatin Calcium40 claims
- Farxiga22 claims
- Amlodipine Besylate19 claims
- Metformin Hcl16 claims
- Citalopram Hbr11 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
- Redwoods Rural Health Center IncRedway, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Karthikeyan Viswanathan among 17,696 internal medicine physician records in California
Karthikeyan Viswanathan, DO 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 2015, is newer than 76% of them.
- NPI issued2015 · 76% of these records are older, 21% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileYes · 63% of these records are
- Graduated2014 · median 2004 among the 11,065 with a school on file
- Record last updated2025 · 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).
29 internal medicine physician records list a practice address in Los Altos
They are 29 of the 718 NPPES records with a practice address in Los Altos, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in Los Altos → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Bhanu-Rekha Bhaskar, MDLos Altos, CA 940221932273539
- Jacqueline Denkabe, MDLos Altos, CA 940221194883520
- Jessica Favreau, MDLos Altos, CA 940221841450731
- Julia Fong, MDLos Altos, CA 940221154409746
- Francis Lastufka, MDLos Altos, CA 940221144312141
- Janusz Madej, M.D.Los Altos, CA 940221376616706
- Carrie Mousseau, M.D.Los Altos, CA 940221447387451
- Amy Muzaffar, MDLos Altos, CA 940221124191481
Common questions
What is Karthikeyan Viswanathan, DO's NPI number?
Karthikeyan Viswanathan, DO's National Provider Identifier (NPI) is 1396128336, issued on Jul 8, 2015. An NPI identifies a provider in billing; it is not a license.
Where is Karthikeyan Viswanathan, DO located?
The NPPES record lists a practice address at 4546 EL Camino Real Ste B7, Los Altos, CA, 94022. Phone: (866) 362-4246. Providers update this record themselves, so call before visiting.
How can I verify Karthikeyan Viswanathan, DO's license?
NPPES lists California license number 20A19044, 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 Karthikeyan Viswanathan, DO prescribe under Medicare Part D?
In 2024, Karthikeyan Viswanathan, DO had 389 Medicare Part D claims for 56 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.