Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum

Mr. Dallas L Mastin, FNP-BC FNP-C

Family Nurse Practitioner in Milford, DE · enumerated 2021.

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

National Provider Identifier

1255929022

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Registry record

Entity type Individual (Type 1)

Name Mr. Dallas L Mastin

Credential FNP-BC FNP-C

Sex Male

Practice address 100 Wellness Way, Milford, DE, 19963

Phone (302) 943-3637

Enumeration date Jan 6, 2021

Last updated in NPPES Aug 9, 2021

Taxonomy & licenses

163W00000X Registered Nurse Nursing Service Providers · License L1-0043517 (DE) Secondary

363LF0000X Family Nurse Practitioner Physician Assistants & Advanced Practice Nursing Providers · License LG-0011570 (DE) Primary

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

How do I verify Dallas Mastin's NPI record?

Cross-check NPI 1255929022 against the official CMS registry at npiregistry.cms.hhs.gov. This page mirrors the same public NPPES data with a monthly snapshot.

Is NPI 1255929022 active?

Yes, as of the latest NPPES snapshot, NPI 1255929022 is active (record last updated 2021-08-09).

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2021-08-09.