Rosa Young Ahn-Horst, MD MPH
Psychiatry Physician · Palo Alto, CA
Rosa Young Ahn-Horst, MD MPH is a psychiatry physician with a practice address in Palo Alto, California, and NPI 1649822420, issued on Jul 12, 2019. Check the license (California A201644, as entered in NPPES) on the Medical Board of California; the Medicare figures below come from public CMS files.
- Name
- Rosa Young Ahn-Horst
- Credential
- MD MPH
- Primary taxonomy
- Psychiatry Physician 2084P0800X
- License number
- A201644 CA
Self-reported in NPPES; status is on the state search - Practice location
- 401 Quarry RD, Palo Alto, CA 94304
- Phone
- (650) 723-5511
- Enumerated
- Jul 12, 2019
- Record last updated
- Jul 27, 2026
- Entity
- Type 1 · individual
8 nearest psychiatry physician records → All 8,673 in California → Look up another NPI →
Also registered at 401 Quarry RD
A shared address usually means a shared clinic or building; it does not show who employs whom.
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- Kelley Anderson, M.S., M.A., PHDPsychologist1851777999
- Robin Apple, PH.D.Psychologist1134284912
- Sahar AshrafzadehPsychiatry Physician1871299230
Verify Rosa Young Ahn-Horst in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersMedical Board of California
Search for license A201644Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
88% fewer Medicare Part D claims than the average psychiatry physician in 2024
122 Medicare Part D claims, against an average of 1,000 among the 35,054 providers of this specialty who prescribed in Part D. Brand-name drugs were 0% of claims.
Most prescribed
- Lurasidone Hcl15 claims
- Bupropion Xl13 claims
- Lithium Carbonate Er13 claims
- Clonazepam11 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.
Rosa Young Ahn-Horst among 8,673 psychiatry physician records in California
Rosa Young Ahn-Horst, MD MPH is one of 8,673 psychiatry physician records with a practice address in California. 67% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does. Its NPI, issued in 2019, is newer than 85% of them.
- NPI issued2019 · 85% of these records are older, 13% newer
- In a Medicare fileYes · 67% of these records are
- In the CMS Doctors and Clinicians fileNo · 38% of these records are
- Record last updated2026 · 54% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 2084P0800X and a California practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
215 psychiatry physician records list a practice address in Palo Alto
They are 215 of the 7,617 NPPES records with a practice address in Palo Alto, and 8,673 psychiatry physician records in California.
All 8,673 in California → Every provider in Palo Alto → Psychiatry Physician nationwide →
The 8 psychiatry physician records with the nearest ZIP codes
- Elias Aboujaoude, MDPalo Alto, CA 943041649209768
- Steven Bagley, MDPalo Alto, CA 943041730125048
- Justin Birnbaum, M.D.Palo Alto, CA 943041013007848
- Kim Bullock, M.D.Palo Alto, CA 943041790842763
- Christopher Capelle, MDPalo Alto, CA 943041902919640
- John Dorfman, M. D.Palo Alto, CA 943041912944687
- Carla Galloway, M.D.Palo Alto, CA 943041790881506
- Robert Hayward, MD, MPHPalo Alto, CA 943041437216744
Common questions
What is Rosa Young Ahn-Horst, MD MPH's NPI number?
Rosa Young Ahn-Horst, MD MPH's National Provider Identifier (NPI) is 1649822420, issued on Jul 12, 2019. An NPI identifies a provider in billing; it is not a license.
Where is Rosa Young Ahn-Horst, MD MPH located?
The NPPES record lists a practice address at 401 Quarry RD, Palo Alto, CA, 94304. Phone: (650) 723-5511. Providers update this record themselves, so call before visiting.
How can I verify Rosa Young Ahn-Horst, MD MPH's license?
NPPES lists California license number A201644, 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 Rosa Young Ahn-Horst, MD MPH prescribe under Medicare Part D?
In 2024, Rosa Young Ahn-Horst, MD MPH had 122 Medicare Part D claims; the average among psychiatry physician prescribers was 1,000. 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.