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DR. ALEXANDER HORWITZ MD
NPI 1891317954
Psychiatry & Neurology - Psychiatry in Napa, CA

Active since May 12, 2020PECOS Enrolled
2100 NAPA VALLEJO HWY, NAPA, CA 94558(707) 253-5000 Get Directions Write a Review

NPPES record last updated: August 10, 2025. Verified against the NPPES registry weekly; last sync: October 18, 2026.

Record update history: Aug 10, 2025, May 6, 2024, Oct 2, 2023 and 1 more (4 updates tracked since 2020).

About Dr. Alexander Horwitz Md NPPES

Official registry information on file with the National Plan and Provider Enumeration System.

DR. ALEXANDER HORWITZ MD (NPI 1891317954) is an individual psychiatry provider in Napa, California, licensed in California (A181639) and active in the NPI registry since May 2020. He is enrolled in Medicare PECOS and maintains 3 additional practice locations.

NPPES Registry Identity

NPI1891317954
Entity TypeIndividualMale
Primary Taxonomy2084P0800X
Provider Legal NameDR. ALEXANDER HORWITZCredential: MD
Location Address2100 NAPA VALLEJO HWYNapa, CA 94558-6234
Mailing Address2100 Napa Vallejo HwyNapa, CA 94558-6234
Phone(707) 253-5000
Sole ProprietorNo
Enumeration DateMay 12, 2020
Last NPPES UpdateAugust 10, 20254 updates tracked since enumeration
NPPES CertifiedAugust 10, 2025
✔ NPI 1891317954 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses 2

★ Primary SpecialtyPsychiatry & Neurology · PsychiatryAllopathic & Osteopathic Physicians
Taxonomy Code2084P0800X
License✔ Licensed in CA · A181639
Definition
A Psychiatrist specializes in the prevention, diagnosis, and treatment of mental disorders, emotional disorders, psychotic disorders, mood disorders, anxiety disorders, substance-related disorders, sexual and gender identity disorders and adjustment disorders. Biologic, psychological, and social components of illnesses are explored and understood in treatment of the whole person. Tools used may include diagnostic laboratory tests, prescribed medications, evaluation and treatment of psychological and interpersonal problems with individuals and families, and intervention for coping with stress, crises, and other problems.
Also ListedStudent in an Organized Health Care Education/Training ProgramTaxonomy 390200000X · License A181639 (CA)
2100 NAPA VALLEJO HWY, Napa, CA 94558
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Secondary Practice Locations 3

Location 1147 N Brent StVentura, CA 93003-2854 · Phone (805) 948-5672
Location 2Hillmont Psychiatric Center, 200 Hillmont AvVentura, CA 93003 · Phone (805) 652-6729
Location 310333 El Camino RealAtascadero, CA 93422-5808 · Phone (805) 468-2000

Medicare Participation & PECOS CMS

Medicare enrollment, assignment, billing reassignment, and ordering and referring status from CMS.

Medicare Enrollment Status

✔

Enrolled in Medicare (PECOS)

Dr. Alexander Horwitz Md is registered in the CMS Provider Enrollment, Chain and Ownership System (PECOS).

Eligible to Order & Refer✔ Part B Labs & Imaging✔ Durable Medical Equipment✔ Home Health Agency✔ Power Mobility DevicesPer the CMS Ordering and Referring file. Eligibility means Medicare pays claims that this provider orders or refers for these categories.

Medicare Billing Reassignment

Medicare enrollment records show Alexander Horwitz reassigns Medicare billing to 1 organization. The organization bills Medicare for the services this provider delivers there.

Department Of State Hospitals
Same address
Psychiatric Hospital
2100 NAPA VALLEJO HWY
Napa, CA 94558
  • Reassigned Medicare billing, California enrollment
  • 755 clinicians in this Medicare group
NPI 1326098161 (707) 253-5000

Source: CMS Revalidation Reassignment List, October 2026 release. Reassignment records can lag staffing changes; confirm a current affiliation with the organization.

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 94558 ZIP code area, from fee-for-service claims. These are area statistics, not this provider’s prices; actual charges vary by service and coverage.

New Patient
$192.16 typical visit price
range $65.08 – $192.16
Typical copayment $48.04 (range $16.27 – $48.04)
Most-billed visit code 99205
Established Patient
$80.32 typical visit price
range $21.86 – $157.83
Typical copayment $20.08 (range $5.46 – $39.45)
Most-billed visit code 99213
Amounts reflect what Medicare beneficiaries in this ZIP area are typically charged for office visits. Patients with other coverage should check their individual plans.

Other Providers at the Same Location NPPES 20

Providers registered at the same practice address, or within the immediate area, according to the NPPES registry.

NAPA VALLEY PROJECT NINETY INC.
Substance Abuse Rehabilitation Facility
2100 NAPA VALLEJO HWY, M-1 M-2
NAPA, CA 94558
Napa County (707) 603-1112
DR. STEVEN JIN CHOI PH.D.
Psychologist (Clinical)
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 254-2712
MR. BENJAMIN JOSEPH LEVIN PSY.D.
Psychologist
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 253-5631
DUSTIN REAGIN PSYD
Psychologist
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (415) 476-3902
BRITTANY ALYCE CUNNINGHAM PH.D.
Psychologist (Clinical)
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 253-5654
ALI AKHAVAN MD
Internal Medicine
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 253-5000
MS. ALICE L SUTTON LCSW
Social Worker (Clinical)
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 253-5120
DR. KRISTOPHER M THOMAS PH.D.
Psychologist
2100 NAPA VALLEJO HWY
NAPA, CA 94558
Napa County (707) 253-5460

Frequently Asked Questions NPPES & CMS

Common questions about this NPI record, answered from the official NPPES registry and CMS datasets shown on this page.

What is Alexander Horwitz's NPI number?

The NPI number for Alexander Horwitz is 1891317954. It was assigned to this individual provider in the NPPES registry on May 12, 2020.

Where is Alexander Horwitz located?

Alexander Horwitz practices at 2100 Napa Vallejo Hwy, Napa, CA 94558. The listed phone number is (707) 253-5000.

What is Alexander Horwitz's specialty?

The primary specialty registered for this NPI is Psychiatry & Neurology, specializing in Psychiatry, with taxonomy code 2084P0800X.

Is Alexander Horwitz enrolled in Medicare?

Yes. Alexander Horwitz is registered in the Medicare PECOS enrollment system.

Which organization bills Medicare for Alexander Horwitz's services?

According to the CMS Revalidation Reassignment List (October 2026 release), Alexander Horwitz reassigns Medicare benefits to Department Of State Hospitals (Napa, CA). The reassignment is filed with Medicare on form CMS-855R, signed by both the clinician and the organization, and lets the organization bill Medicare and receive payment for Alexander Horwitz's services. Reassignment records can lag staffing changes; confirm current arrangements with the organization.

When was this NPI record last updated?

The NPPES record for Alexander Horwitz was last updated on August 10, 2025. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 14 months ago. If this record has changed at CMS more recently, you can request an on-demand re-check against the live CMS registry, directly from this page.