William L. Matzner, M.D., PH.D.

Primary specialty

Internal Medicine PhysicianTaxonomy code 207R00000X

License

AO43053 Issued in CA

Practice address

543 Country Club Dr # B125
Simi Valley, CA 93065-0637

Phone

(805) 578-7000

NPI assigned

Dec 8, 2006

Last updated

Sep 27, 2026By the provider in NPPES

Sex

Male

Sole proprietor

Yes

Registry information is reported by the provider to CMS and is not verified. About this source

Specialties & licenses 1

Addresses

Medicare fee-for-service enrollment

Not listed in the public Medicare enrollment file

Medicare enrollment (NPD)

Not enrolled

HHS exclusion list flag

Flagged The directory lists this NPI on an HHS exclusion list. Confirm with the OIG exclusions search.

Credentials

Doctor of Medicine, Doctor of Philosophy

State licenses

Practice roles

Organizations this provider is connected to: Medicare benefit reassignments (the organization bills Medicare for this provider’s services), Care Compare group memberships, National Provider Directory roles and organizations whose NPPES authorized official is this provider.

• Orion Medical Group

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  • NPI 1710145164
  NPD (past) Authorized official
• Tony Makhlouf MD Inc

  • Rheumatology Physician
  • Simi Valley, CA
  • NPI 1467995951
  NPD (past)

The complete NPPES record for this NPI in the NPI Registry API format.

{
    "created_epoch": "1165536000000",
    "enumeration_type": "NPI-1",
    "last_updated_epoch": "1790467200000",
    "number": "1306905716",
    "addresses": [
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "MAILING",
            "address_type": "DOM",
            "address_1": "543 COUNTRY CLUB DR # B125",
            "city": "SIMI VALLEY",
            "state": "CA",
            "postal_code": "930650637",
            "telephone_number": "805-578-7000",
            "fax_number": "805-578-7005"
        },
        {
            "country_code": "US",
            "country_name": "United States",
            "address_purpose": "LOCATION",
            "address_type": "DOM",
            "address_1": "543 COUNTRY CLUB DR # B125",
            "city": "SIMI VALLEY",
            "state": "CA",
            "postal_code": "930650637",
            "telephone_number": "805-578-7000"
        }
    ],
    "practiceLocations": [],
    "basic": {
        "last_name": "MATZNER",
        "first_name": "WILLIAM",
        "middle_name": "L.",
        "credential": "M.D., PH.D.",
        "sole_proprietor": "YES",
        "sex": "M",
        "enumeration_date": "2006-12-08",
        "last_updated": "2026-09-27",
        "certification_date": "2026-09-27",
        "status": "A"
    },
    "taxonomies": [
        {
            "code": "207R00000X",
            "taxonomy_group": "",
            "desc": "Internal Medicine",
            "state": "CA",
            "license": "AO43053",
            "primary": true
        }
    ],
    "identifiers": [],
    "endpoints": [],
    "other_names": []
}

• Matei T Tocuseanu DDS, Inc
• Lilia Matevosyan
• Petcharin Mathison
• Mattbahardds Inc
• Michael Matuszak
• Maxi-Med Supples, Inc (Maxi-Med Supples)
• Cho May, M.D
• Maziar Izadi DDS Inc (Family Dental Care)
• Brenda Margaret McAlpin, PA-C
• Liana L McCoy, LCSW

• Internal Medicine Physician in Simi Valley, CA
• Providers in Simi Valley, CA by specialty
• Internal Medicine Physician in California

• NPPES NPI Registry (CMS): identity, addresses, specialties, licenses, identifiers and endpoints. Last updated by the provider on Sep 27, 2026; self-reported and not verified by CMS. Specialty names from the NUCC taxonomy.
• Medicare enrollment (CMS PECOS): enrollments, PAC IDs and benefit reassignments; OIG LEIE.
• National Provider Directory (CMS): practice roles, locations, licenses, networks and endpoints.

Verify at the official NPI Registry.