Karthikeyan Viswanathan, DO
NPI 1396128336 · Internal Medicine Physician · Los Altos, CA
Enrolled with Medicare as Practitioner - Internal Medicine · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Karthikeyan Viswanathan, DO is a Internal Medicine Physician provider in Los Altos, CA (NPI 1396128336).
Provider details
- NPI number
- 1396128336
- Entity type
- Individual
- Primary specialty
- Internal Medicine PhysicianAllopathic & Osteopathic Physicians
- Credential
- DO
- Sex
- Male
- Sole proprietor
- No
- License
- 20A19044 (CA)
Specialties & taxonomies
Allopathic & Osteopathic Physicians
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure28% of score
10 yrs in NPPES registry
- Profile completeness28% of score
100% of core fields populated
- Practice footprint17% of score
1 documented practice location
- Medicare service volume (vs. specialty peers)28% of score
27 Medicare services, 2024 (ranked within specialty)
Medicare volume is ranked against active providers in the same specialty. Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
What this provider does (Medicare)
Based on Medicare fee-for-service claims, 2024; not all care is captured.
| Service (HCPCS) | Medicare services | Typical Medicare-allowed (2024) |
|---|---|---|
| Hemoglobin A1c Level83036 | 14 | $10 |
| Automated Urinalysis Test81003 | 13 | $2 |
Typical Medicare-allowed amounts for these services range $2–$10 (2024). The Medicare-allowed amount is what Medicare recognizes for a service under fee-for-service — a reference figure for 2024, not a price quote and not what you would be billed. Medicare Part B covers roughly an eighth of all NPIs (65+ skew); services with fewer than 11 beneficiaries are suppressed by CMS. Source: CMS Medicare Physician & Other Practitioners, by Provider & Service.
What this provider prescribes (Medicare Part D)
Top drugs by Medicare Part D claim volume, 2024 · 6 distinct drugs on file.
| Drug | Part D claims (2024) | Beneficiaries |
|---|---|---|
| Lisinopril | 44 | 14 |
| Atorvastatin Calcium | 40 | 11 |
| Dapagliflozin Propanediolbrand: Farxiga | 22 | — |
| Amlodipine Besylate | 19 | — |
| Metformin Hcl | 16 | — |
| Citalopram Hydrobromidebrand: Citalopram Hbr | 11 | — |
Practice location
Mailing address
Registry dates
- Enumerated
- 2015-07-08
- Last updated
- 2025-08-21
- Certified
- 2025-08-21
Frequently asked questions
- What is Karthikeyan Viswanathan's NPI number?
- Karthikeyan Viswanathan's National Provider Identifier (NPI) is 1396128336, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Karthikeyan Viswanathan's specialty?
- Karthikeyan Viswanathan is listed in the NPPES registry with a primary specialty of Internal Medicine Physician (Allopathic & Osteopathic Physicians).
- Where is Karthikeyan Viswanathan located?
- Karthikeyan Viswanathan's practice location on file with NPPES is 4546 El Camino Real Ste B7, Los Altos, CA 94022-1069.
- What is Karthikeyan Viswanathan's phone number?
- The practice phone number listed in the NPPES registry for Karthikeyan Viswanathan is (866) 362-4246.
- Does Karthikeyan Viswanathan accept Medicare?
- Karthikeyan Viswanathan is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Karthikeyan Viswanathan's NPI active?
- Yes — Karthikeyan Viswanathan's NPI (1396128336) is active in the NPPES registry as of the last update on 2025-08-21.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.