Marianna Grennan, LCSW R
NPI 1013188390 · Clinical Social Worker · Melville, NY
Enrolled with Medicare as Practitioner - Clinical Social Worker · source: CMS PECOS Public Provider Enrollment (2026.04.01)
Marianna Grennan, LCSW R is a Clinical Social Worker provider in Melville, NY (NPI 1013188390).
Provider details
- NPI number
- 1013188390
- Entity type
- Individual
- Primary specialty
- Clinical Social WorkerBehavioral Health & Social Service Providers
- Credential
- LCSW R
- Sex
- Female
- Sole proprietor
- Yes
- License
- R049385 (NY)
Specialties & taxonomies
Behavioral Health & Social Service Providers
Profile Score
A profile completeness & documented-activity index — NOT a quality, outcomes, or patient-satisfaction rating.
- Registry tenure38% of score
18 yrs in NPPES registry
- Profile completeness38% of score
100% of core fields populated
- Practice footprint23% of score
1 documented practice location
Signals a provider has no public data for (e.g. Medicare claims) are left out of the score entirely — never counted as zero — so providers without that data are not penalized. See the full formula and weights in our methodology.
Practice location
Mailing address
Registry dates
- Enumerated
- 2008-03-14
- Last updated
- 2008-03-14
Frequently asked questions
- What is Marianna Grennan's NPI number?
- Marianna Grennan's National Provider Identifier (NPI) is 1013188390, a unique 10-digit ID issued by CMS for use in standard healthcare transactions.
- What is Marianna Grennan's specialty?
- Marianna Grennan is listed in the NPPES registry with a primary specialty of Clinical Social Worker (Behavioral Health & Social Service Providers).
- Where is Marianna Grennan located?
- Marianna Grennan's practice location on file with NPPES is 900 Walt Whitman Road, Melville, NY 11747.
- What is Marianna Grennan's phone number?
- The practice phone number listed in the NPPES registry for Marianna Grennan is (631) 271-5617.
- Does Marianna Grennan accept Medicare?
- Marianna Grennan is approved to bill Medicare according to CMS PECOS enrollment data (2026.04.01). Confirm current participation with the provider before scheduling.
- Is Marianna Grennan's NPI active?
- Yes — Marianna Grennan's NPI (1013188390) is active in the NPPES registry as of the last update on 2008-03-14.
Source: CMS NPPES Data Dissemination (June 2026). NPI Central is not affiliated with CMS. Data is provided as-is from the public registry.