William B. Gregory, MD
Emergency Medicine Physician · Pasadena, CA
William B. Gregory, MD is an emergency medicine physician with a practice address in Pasadena, California, and NPI 1659337350, issued on Apr 22, 2006. Check the license (California A78714, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- William B. Gregory
- Credential
- MD
- Primary taxonomy
- Emergency Medicine Physician 207P00000X
- License number
- A78714 CA
Self-reported in NPPES; status is on the state search - Practice location
- 100 W California Blvd, Pasadena, CA 91105
- Phone
- (626) 397-3445
- Enumerated
- Apr 22, 2006
- Record last updated
- Jun 13, 2008 (not updated in 18 years: call before relying on the address or phone)
- Fax
- (626) 397-5643
- Medicaid ID
- OOA787140 CA
- Medicare enrollment
- Enrolled (PECOS I20140602001903); accepts Medicare assignment
- Medical or professional school
- Medical University Of South Carolina College Of Medicine, 1999
- Entity
- Type 1 · individual
8 nearest emergency medicine physician records → All 7,751 in California → Look up another NPI →
Also registered at 100 W California Blvd
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Devan Abhari, MDStudent in an Organized Health Care Education/Training Program1922849041
- Lina Acopians, DOHospitalist Physician1548821523
- Daniel Adran, MDNeuroradiology Physician1518456441
- Alipasha Adrangui, M.D.Hospitalist Physician1780911263
- Vahe Aghajanyan, M.D.Student in an Organized Health Care Education/Training Program1447047238
- Ignacio Aguilar, RNFARegistered Nurse First Assistant1497583603
Verify William B. Gregory in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A78714Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
50% fewer Medicare Part D claims than the average emergency medicine physician in 2024
112 Medicare Part D claims for 76 beneficiaries, against an average of 226 among the 54,106 providers of this specialty who prescribed in Part D. Brand-name drugs were 14% of claims.
Most prescribed
- Prednisone19 claims
- Amoxicillin-Clavulanate Potass15 claims
- Albuterol Sulfate Hfa13 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 2 group practices
- Hospitalist Medicine Physicians OF Texas - Cypress PLLCBonham, TX
- Third Coast Emergency Physicians Southwest PASan Antonio, TX
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
William B. Gregory among 7,751 emergency medicine physician records in California
William B. Gregory, MD is one of 7,751 emergency medicine physician records with a practice address in California. 81% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2006, is newer than 4% of them.
- NPI issued2006 · 4% of these records are older, 60% newer
- In a Medicare fileYes · 81% of these records are
- In the CMS Doctors and Clinicians fileYes · 59% of these records are
- Graduated1999 · median 2011 among the 4,560 with a school on file
- Record last updated2008 · 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 207P00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Emergency Medicine Physician providers in California
There are 7,751 emergency medicine physician records in California.
All 7,751 in California → Every provider in Pasadena → Emergency Medicine Physician nationwide →
The 8 emergency medicine physician records with the nearest ZIP codes
- Betty Ahn, MDPasadena, CA 911051902862089
- Roy Antelyes, M.D.Pasadena, CA 911051275648610
- Timothy Ballard, M.D.Pasadena, CA 911051710090816
- Bradley Gerberich, M.D.Pasadena, CA 911051790728277
- Stanley Kalter, MDPasadena, CA 911051518071125
- Taline Kilaghbian, M.D.Pasadena, CA 911051699889212
- Mai Lai, MDPasadena, CA 911051841232717
- Brandon Lew, D.O.Pasadena, CA 911051851405203
Common questions
What is William B. Gregory, MD's NPI number?
William B. Gregory, MD's National Provider Identifier (NPI) is 1659337350, issued on Apr 22, 2006. An NPI identifies a provider in billing; it is not a license.
Where is William B. Gregory, MD located?
The NPPES record lists a practice address at 100 W California Blvd, Pasadena, CA, 91105. Phone: (626) 397-3445. Providers update this record themselves, so call before visiting.
How can I verify William B. Gregory, MD's license?
NPPES lists California license number A78714, 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 B. Gregory, MD prescribe under Medicare Part D?
In 2024, William B. Gregory, MD had 112 Medicare Part D claims for 76 beneficiaries; the average among emergency medicine physician prescribers was 226. 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.