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Dr. William Sprague Trask IV, D.O.

Anesthesiology Physician in Boulder, CO · enumerated 2006.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1184706608

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Registry record

Entity type Individual (Type 1)
Name Dr. William Sprague Trask IV
Credential D.O.
Sex Male
Practice address 4747 Arapahoe Ave, Boulder, CO, 80303
Phone (303) 415-2532
Fax (303) 785-1725
Enumeration date Oct 20, 2006
Last updated in NPPES Mar 2, 2019

Taxonomy & licenses

207L00000X Anesthesiology Physician Allopathic & Osteopathic Physicians · License OL20000111 (WA) Secondary
207L00000X Anesthesiology Physician Allopathic & Osteopathic Physicians · License OP60150344 (WA) Secondary
207L00000X Anesthesiology Physician Allopathic & Osteopathic Physicians · License 49491 (CO) Primary
DO — Doctor of Osteopathic Medicine: A fully licensed physician trained in osteopathic medical schools, with the same practice rights as an MD. About the DO credential

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes — even if the provider moves or changes specialty.

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Frequently asked questions

What specialty is William Trask?
William Trask is registered in NPPES with the primary taxonomy of Anesthesiology Physician. The taxonomy code describes the provider's classification and area of specialization for claims and credentialing.
Is this the official NPI registry?
No. NPI Portal is a private site built on public CMS NPPES data. The official registry is npiregistry.cms.hhs.gov, operated by CMS.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2019-03-02.