Dr. Mark Stephen Lum, PSY.D.

Dr. Mark Stephen Lum is a Clinical Psychologist provider (Psychologist) practicing in Orange, CA, registered in the NPPES registry with NPI 1083648752 since 2006. The credential PSYD stands for Doctor of Psychology. Practices at Mark Lum Psychological Services (listed at the same practice address in NPPES).

✓ Active NPI ✓ Valid NPI checksum Sole proprietor

NPI	1083648752
Entity type	Individual (Type 1)
Name	Dr. Mark Stephen Lum
Credential	PSY.D.
Sex	Male
Practice address	Orange, CA, 92865
Phone	7142829713
Fax	7142828016
Enumeration date	2006-07-10
Last updated in NPPES	2007-09-20

Street address withheld — NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

Taxonomy code	Specialty	Primary	License	State
103TC0700X	Clinical Psychologist	Primary	PSY13344	CA

PSYD — Doctor of Psychology: A clinical doctorate in psychology focused on professional practice. About the PSYD credential

Copy-ready billing details

Provider: Mark Lum, PSY.D.
NPI: 1083648752
Taxonomy: 103TC0700X (Clinical Psychologist)
Address: Orange, CA, 92865

Other providers at this practice address

NPI	Name	Type	Specialty	Location
1992986616	Mark Lum Psychological Services	Organization	Clinical Psychologist	Orange, CA
1558685859	Thomas Lester	Individual	Psychiatry Physician	Orange, CA

Verify this record

Cross-check NPI 1083648752 against the authoritative CMS record: view Dr. Mark Stephen Lum on the official NPPES registry .

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 or validate an NPI number.

Frequently asked questions

What specialty is Mark Lum?

Mark Lum is registered in NPPES with the primary taxonomy of Clinical Psychologist. 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.

Source: CMS NPPES (public data). Snapshot 2026-07-11. Provider record last updated 2007-09-20.