Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Dr. Mark Thomas O'Hollaren, M.D.

Allergy Physician in Portland, OR · enumerated 2006.

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

National Provider Identifier

1588723787

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Registry record

Entity type Individual (Type 1)

Name Dr. Mark Thomas O'Hollaren

Credential M.D.

Sex Male

Practice address 511 Sw 10th Ave, Suite 1301, Portland, OR, 97205

Phone (503) 228-0155

Fax (503) 226-8342

Enumeration date Dec 6, 2006

Last updated in NPPES Jul 8, 2007

Taxonomy & licenses

207KA0200X Allergy Physician Allopathic & Osteopathic Physicians · License 13450 (OR) Primary

MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

Other identifiers

Identifier	Type	State	Issuer
167155	Medicaid	OR	-

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.

Read the full guide → Validate an NPI →

Frequently asked questions

Is NPI 1588723787 active?

Yes, as of the latest NPPES snapshot, NPI 1588723787 is active (record last updated 2007-07-08).

How do I verify Mark O'Hollaren's NPI record?

Cross-check NPI 1588723787 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-07-08.