Justin Mager, M.D.
Internal Medicine Physician · Mill Valley, CA
Justin Mager, M.D. is an internal medicine physician with a practice address in Mill Valley, California, and NPI 1669672739, issued on Jul 18, 2007. Check the license (California A95972, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Justin Mager
- Credential
- M.D.
- Primary taxonomy
- Internal Medicine Physician 207R00000X
- License number
- A95972 CA
Self-reported in NPPES; status is on the state search - Practice location
- 239 Miller Ave, Mill Valley, CA 94941
- Phone
- (415) 730-4235
- Enumerated
- Jul 18, 2007
- Record last updated
- Nov 5, 2012 (not updated in 14 years: call before relying on the address or phone)
- Fax
- (415) 952-9345
- Entity
- Type 1 · individual
Also registered at 239 Miller Ave
A shared address usually means a shared clinic or building; it does not show who employs whom.
- Susan Chappell, RN,MSN,FNP-BCFamily Nurse Practitioner1528493822
- Christine Donohue, M.A.Marriage & Family Therapist1902939234
- Nancy Jacobs, LCSWClinical Social Worker1225173982
- Frances Yankie, DDSGeneral Practice Dentistry1629109814
Verify Justin Mager in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A95972Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
93% fewer Medicare Part D claims than the average internal medicine physician in 2024
235 Medicare Part D claims for 26 beneficiaries, against an average of 3,176 among the 108,855 providers of this specialty who prescribed in Part D.
Most prescribed
- Losartan Potassium34 claims
- Rosuvastatin Calcium24 claims
- Synthroid13 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.
14 internal medicine physician records list a practice address in Mill Valley
They are 14 of the 653 NPPES records with a practice address in Mill Valley, and 17,696 internal medicine physician records in California.
All 14 in Mill Valley → All 17,696 in California → Every provider in Mill Valley →
Other internal medicine physician records in California
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- Alistair Aaronson, MDStanford, CA1457628760
- Jose Abad., MDSacramento, CA1144607219
- Donna Abare, MDOakland, CA1386722155
- Marce AbareScotts Valley, CA1457744708
- Samuel Abarte, M.D.Chula Vista, CA1578535498
- Alexander Abary, MDLong Beach, CA1104995919
- Luba Abascal, MDSan Francisco, CA1023180874
- Michael Abate, MDSacramento, CA1548248131
- Wali Abawi, D.O.Joshua Tree, CA1104362268
Common questions
What is Justin Mager, M.D.'s NPI number?
Justin Mager, M.D.'s National Provider Identifier (NPI) is 1669672739, issued on Jul 18, 2007. An NPI identifies a provider in billing; it is not a license.
Where is Justin Mager, M.D. located?
The NPPES record lists a practice address at 239 Miller Ave, Mill Valley, CA, 94941. Phone: (415) 730-4235. Providers update this record themselves, so call before visiting.
How can I verify Justin Mager, M.D.'s license?
NPPES lists California license number A95972, 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 Justin Mager, M.D. prescribe under Medicare Part D?
In 2024, Justin Mager, M.D. had 235 Medicare Part D claims for 26 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.