John Massaro, DO
Internal Medicine Physician · San Luis Obispo, CA
John Massaro, DO is an internal medicine physician with a practice address in San Luis Obispo, California, and NPI 1588665293, issued on Aug 3, 2005. Check the license (California 20A7971, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- John Massaro
- Credential
- DO
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- 20A7971 CA
Self-reported in NPPES; status is on the state search - Practice location
- 975 Osos St, San Luis Obispo, CA 93401
- Phone
- (805) 549-0677
- Enumerated
- Aug 3, 2005
- Record last updated
- Nov 30, 2011 (not updated in 15 years: call before relying on the address or phone)
- Entity
- Type 1 · individual
8 nearest internal medicine physician records → All 17,696 in California → Look up another NPI →
Verify John Massaro in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A7971Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
95% fewer Medicare Part D claims than the average internal medicine physician in 2024
154 Medicare Part D claims for 57 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Most prescribed
- Eliquis11 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.
John Massaro among 17,696 internal medicine physician records in California
John Massaro, 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 2005, is newer than 0% of them.
- NPI issued2005 · 0% of these records are older, 95% newer
- In a Medicare fileYes · 79% of these records are
- In the CMS Doctors and Clinicians fileNo · 63% of these records are
- Record last updated2011 · 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).
41 internal medicine physician records list a practice address in San Luis Obispo
They are 41 of the 3,403 NPPES records with a practice address in San Luis Obispo, and 17,696 internal medicine physician records in California.
All 17,696 in California → Every provider in San Luis Obispo → Internal Medicine Physician nationwide →
The 8 internal medicine physician records with the nearest ZIP codes
- Jeffrey Bloom, MDSan Luis Obispo, CA 934011154346377
- Deborah Cherry, M.D.San Luis Obispo, CA 934011063495356
- Grace Crittenden, MDSan Luis Obispo, CA 934011053343764
- Mark Donaldson, M.D.San Luis Obispo, CA 934011710923933
- Maureen Haas, M.D.San Luis Obispo, CA 934011760437230
- Stephen Hansen, MDSan Luis Obispo, CA 934011649200742
- Jana Hanson, MDSan Luis Obispo, CA 934011508849894
- Leslie Michel, MDSan Luis Obispo, CA 934011184670820
Common questions
What is John Massaro, DO's NPI number?
John Massaro, DO's National Provider Identifier (NPI) is 1588665293, issued on Aug 3, 2005. An NPI identifies a provider in billing; it is not a license.
Where is John Massaro, DO located?
The NPPES record lists a practice address at 975 Osos St, San Luis Obispo, CA, 93401. Phone: (805) 549-0677. Providers update this record themselves, so call before visiting.
How can I verify John Massaro, DO's license?
NPPES lists California license number 20A7971, 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 John Massaro, DO prescribe under Medicare Part D?
In 2024, John Massaro, DO had 154 Medicare Part D claims for 57 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.