William Norman Hamstra, D.O.
Surgery Physician · San Ramon, CA
William Norman Hamstra, D.O. is a surgery physician with a practice address in San Ramon, California, and NPI 1306835723, issued on Oct 18, 2005. Check the license (California 20A5413, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- William Norman Hamstra
- Credential
- D.O.
- Primary taxonomy
- Surgery Physician 208600000X
- License number
- 20A5413 CA
Self-reported in NPPES; status is on the state search - Practice location
- 2305 Camino Ramon, San Ramon, CA 94583
- Phone
- (925) 447-0660
- Enumerated
- Oct 18, 2005
- Record last updated
- Feb 11, 2022
- Fax
- (925) 443-7506
- Medicaid ID
- 00AX54131 CA
- Medicare enrollment
- Enrolled (PECOS I20050725000773); accepts Medicare assignment
- Medical or professional school
- Oklahoma State University College Of Osteopathic Medicine, 1986
- Entity
- Type 1 · individual
8 nearest surgery physician records → All 3,118 in California → Look up another NPI →
Also registered at 2305 Camino Ramon
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify William Norman Hamstra in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license 20A5413Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
49% fewer Medicare Part D claims than the average surgery physician in 2024
75 Medicare Part D claims for 40 beneficiaries, against an average of 147 among the 20,115 providers of this specialty who prescribed in Part D. 32 claims were for opioids.
Most prescribed
- Oxycodone Hcl26 claims
- Ibuprofen18 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
- Permanente Medical Group IncStockton, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
William Norman Hamstra among 3,118 surgery physician records in California
William Norman Hamstra, D.O. is one of 3,118 surgery physician records with a practice address in California. 75% 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, 94% newer
- In a Medicare fileYes · 75% of these records are
- In the CMS Doctors and Clinicians fileYes · 61% of these records are
- Graduated1986 · median 2003 among the 1,901 with a school on file
- Record last updated2022 · 59% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 208600000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Surgery Physician providers in California
There are 3,118 surgery physician records in California.
All 3,118 in California → Every provider in San Ramon → Surgery Physician nationwide →
The 8 surgery physician records with the nearest ZIP codes
- Ron Cooper, M.D.San Ramon, CA 945831407941933
- Barry Gardiner, M.D.San Ramon, CA 945831619068533
- Aileen Murphy, D.O.San Ramon, CA 945831053616482
- Michael Wynn, MDSan Ramon, CA 945831285673996
- Jing Zhou, M.D.San Ramon, CA 945831760703078
- James Bryant, MDSan Leandro, CA 945781750454708
- Garfield Bryant, M.D.San Leandro, CA 945781952402109
- Chau Dang, MDPleasanton, CA 945881649213398
Common questions
What is William Norman Hamstra, D.O.'s NPI number?
William Norman Hamstra, D.O.'s National Provider Identifier (NPI) is 1306835723, issued on Oct 18, 2005. An NPI identifies a provider in billing; it is not a license.
Where is William Norman Hamstra, D.O. located?
The NPPES record lists a practice address at 2305 Camino Ramon, San Ramon, CA, 94583. Phone: (925) 447-0660. Providers update this record themselves, so call before visiting.
How can I verify William Norman Hamstra, D.O.'s license?
NPPES lists California license number 20A5413, 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 William Norman Hamstra, D.O. prescribe under Medicare Part D?
In 2024, William Norman Hamstra, D.O. had 75 Medicare Part D claims for 40 beneficiaries; the average among surgery physician prescribers was 147. 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.