Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of August 10, 2026.

Mark Glenn Willoughby

Individual provider Addiction (Substance Use Disorder) Counselor · NPI 1174038756

Mark Glenn Willoughby is an Addiction (Substance Use Disorder) Counselor in El Monte, California. Registered with an NPI since 2017.

In the registry since
2017

Practice location Address checks out

3430 Cogswell Rd
El Monte, CA 91732-2785
Phone: (626) 453-3400
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Addiction (Substance Use Disorder) Counselor (primary) Taxonomy 101YA0400X

Record details

NPI number1174038756
Entity typeIndividual (Type 1)
GenderMale
Sole proprietorNo
NPI enumeratedDecember 5, 2017
Last updated in NPPESDecember 5, 2017
Mailing address3430 Cogswell Rd, El Monte, CA 91732-2785

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