Gregory S. Arent, MD
Hospitalist Physician · San Rafael, CA
Gregory S. Arent, MD is a hospitalist physician with a practice address in San Rafael, California, and NPI 1245314210, issued on Oct 25, 2006. Check the license (California A62131, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Gregory S. Arent
- Credential
- MD
- Primary taxonomy
- Hospitalist Physician 208M00000X
- License number
- A62131 CA
Self-reported in NPPES; status is on the state search - Practice location
- 99 Montecillo RD, San Rafael, CA 94903
- Phone
- (415) 444-2000
- Enumerated
- Oct 25, 2006
- Record last updated
- Dec 13, 2021 (not updated in 5 years: call before relying on the address or phone)
- Medicaid ID
- 00A621310 CA
- Medicare enrollment
- Enrolled (PECOS I20110127000121); accepts Medicare assignment
- Medical or professional school
- University Of California, San Francisco School Of Medicine, 1995
- Entity
- Type 1 · individual
8 nearest hospitalist physician records → All 3,099 in California → Look up another NPI →
Also registered at 99 Montecillo RD
A shared address usually means a shared clinic or building; it does not show who employs whom.
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Verify Gregory S. Arent in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A62131Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
24% more Medicare Part D claims than the average hospitalist physician in 2024
644 Medicare Part D claims for 216 beneficiaries, against an average of 521 among the 21,613 providers of this specialty who prescribed in Part D. Brand-name drugs were 9% of claims. 33 claims were for opioids.
Most prescribed
- Atorvastatin Calcium26 claims
- Oxycodone Hcl26 claims
- Pantoprazole Sodium25 claims
- Furosemide23 claims
- Cefadroxil22 claims
- Potassium Chloride22 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 IncVallejo, CA
Source: CMS Doctors and Clinicians National Downloadable File (the group practices a clinician bills Medicare through) (data.cms.gov).
Gregory S. Arent among 3,099 hospitalist physician records in California
Gregory S. Arent, MD is one of 3,099 hospitalist physician records with a practice address in California. 90% 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 2% of them.
- NPI issued2006 · 2% of these records are older, 73% newer
- In a Medicare fileYes · 90% of these records are
- In the CMS Doctors and Clinicians fileYes · 81% of these records are
- Graduated1995 · median 2010 among the 2,505 with a school on file
- Record last updated2021 · 49% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 208M00000X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
Hospitalist Physician providers in California
There are 3,099 hospitalist physician records in California.
All 3,099 in California → Every provider in San Rafael → Hospitalist Physician nationwide →
The 8 hospitalist physician records with the nearest ZIP codes
- Ingrid Brennan, MDSan Rafael, CA 949031518046655
- Anne-Maree Cantwell, MDSan Rafael, CA 949031679657670
- Siraphob Chansangavej, MDSan Rafael, CA 949031386268027
- Viet Lam, MDSan Rafael, CA 949031942384011
- Jeffrey Lovold, MDSan Rafael, CA 949031376627356
- Robert Lowell, MDSan Rafael, CA 949031053495051
- Stephen Mizroch, MDSan Rafael, CA 949031225112394
- Peter Reidy, MDSan Rafael, CA 949031013113257
Common questions
What is Gregory S. Arent, MD's NPI number?
Gregory S. Arent, MD's National Provider Identifier (NPI) is 1245314210, issued on Oct 25, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Gregory S. Arent, MD located?
The NPPES record lists a practice address at 99 Montecillo RD, San Rafael, CA, 94903. Phone: (415) 444-2000. Providers update this record themselves, so call before visiting.
How can I verify Gregory S. Arent, MD's license?
NPPES lists California license number A62131, 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 Gregory S. Arent, MD prescribe under Medicare Part D?
In 2024, Gregory S. Arent, MD had 644 Medicare Part D claims for 216 beneficiaries; the average among hospitalist physician prescribers was 521. 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.