Recently Updated NPI Information — some details in this NPI profile have been updated in the NPI registry within the last 60 days.

ALEXANDER WILLIAM THRELFALL MD
NPI 1669538187
Psychiatry & Neurology - Psychiatry in San Rafael, CA

Q: What is Alexander Threlfall's NPI number?

The NPI number for Alexander Threlfall is 1669538187. It was assigned to this individual provider in the NPPES registry on December 29, 2006.

Q: What is Alexander Threlfall's specialty?

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

Active since December 29, 2006PECOS Enrolled

800 A ST, SAN RAFAEL, CA 94901(415) 457-8182(415) 457-7471 Get Directions Write a Review

NPPES record last updated: September 1, 2026. Verified against the NPPES registry weekly; last sync: September 20, 2026.

Record update history: Sep 1, 2026, Aug 15, 2019, Sep 15, 2016 (3 updates tracked since 2016).

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About Alexander William Threlfall Md NPPES

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

ALEXANDER WILLIAM THRELFALL MD (NPI 1669538187) is an individual psychiatry provider in San Rafael, California, licensed in California (113086) and active in the NPI registry since December 2006. He is enrolled in Medicare PECOS and is a graduate of Other (2006).

NPPES Registry Identity

NPI1669538187

Entity TypeIndividualMale

Primary Taxonomy2084P0800X

Provider Legal NameALEXANDER WILLIAM THRELFALLCredential: MD

Location Address800 A STSan Rafael, CA 94901-3011

Mailing AddressPo Box 3517San Rafael, CA 94912-3517 · (415) 457-8182 · Fax (415) 457-7471

Phone(415) 457-8182

Fax(415) 457-7471

Sole ProprietorNo

Medical School CMSOtherGraduated 2006

Enumeration DateDecember 29, 2006

Last NPPES UpdateSeptember 1, 20263 updates tracked since enumeration

NPPES CertifiedSeptember 1, 2026

✔ NPI 1669538187 is a valid, active identifier and passes the ISO check-digit test.

Specialties & Licenses

★ Primary SpecialtyPsychiatry & Neurology · PsychiatryAllopathic & Osteopathic Physicians

Taxonomy Code2084P0800X

License✔ Licensed in CA · 113086

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.

800 A ST, San Rafael, CA 94901

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Medicare Participation & PECOS CMS

Medicare enrollment, assignment, and ordering and referring status from the CMS PECOS system.

Medicare Enrollment Status

✔

Enrolled in Medicare (PECOS)

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

PECOS PAC ID6103113857

PECOS Enrollment IDI20241007001635

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.

Physician Visit Costs CMS claims · ZIP area

Typical Medicare office-visit costs in the 94901 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

$202.63 typical visit price

range $69.07 – $202.63

Typical copayment $50.65 (range $17.26 – $50.65)

Most-billed visit code 99205

Established Patient

$85.00 typical visit price

range $23.44 – $166.64

Typical copayment $21.25 (range $5.86 – $41.66)

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 14

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

ALYSSA AMBER LAKE

Counselor (Addiction (Substance Use Disorder))

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 847-8733

SHANNALEAH SHAHEDI MASTERS

Physician Assistant

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

OLIVIA HORAN AGPCNP-C

Nurse Practitioner

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

KELLY MCKOIN PA-C

Physician Assistant

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

AGUSTINA DEL CARRIL

Social Worker (Clinical)

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

RITTER CENTER

Clinic/Center (Federally Qualified Health Center (FQHC))

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

MR. MICHAEL A BEYER LCSW

Social Worker (Clinical)

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

PATRICK LIANG PMHNP

Nurse Practitioner (Psychiatric/Mental Health)

800 A ST
SAN RAFAEL, CA 94901

Marin County (415) 457-8182

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 Threlfall's NPI number?

The NPI number for Alexander Threlfall is 1669538187. It was assigned to this individual provider in the NPPES registry on December 29, 2006.

Where is Alexander Threlfall located?

Alexander Threlfall practices at 800 A St, San Rafael, CA 94901. The listed phone number is (415) 457-8182.

What is Alexander Threlfall's specialty?

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

Is Alexander Threlfall enrolled in Medicare?

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

When was this NPI record last updated?

The NPPES record for Alexander Threlfall was last updated on September 1, 2026. NPI Profile syncs weekly with the NPPES registry data releases published by CMS. This NPI record was last updated 27 days 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.