OLIVIA CROSBY-GAGNIER
NPI 1578450599
Counselor - Mental Health in West Chester, PA

NPI Status: Active since June 23, 2025

Contact Information

142 W MARKET ST
WEST CHESTER, PA
ZIP 19382
Phone: (610) 616-5890

NPI Profile Information
Primary Taxonomy
NPI Validation
Other Providers Same Location
Frequently Asked Questions

Individual
Female
Counselor
Mental Health

About OLIVIA CROSBY-GAGNIER

This page provides the complete NPI Profile along with additional information for Olivia Crosby-gagnier, a provider established in West Chester, Pennsylvania with a medical specialization in Counselor, focusing in mental health . The healthcare provider is registered in the NPI registry with number 1578450599 assigned on June 2025. The practitioner's primary taxonomy code is 101YM0800X. The provider is registered as an individual and her NPI record was last updated March 2026.

NPI: 1578450599
Provider Name: OLIVIA CROSBY-GAGNIER
Gender: Female
Entity Type: Individual
Location Address: 142 W MARKET ST WEST CHESTER, PA 19382
Location Phone: (610) 616-5890
Mailing Address: 1011 STIRLING ST COATESVILLE, PA 19320
Mailing Phone: (484) 667-6985
Is Sole Proprietor?: Yes
Enumeration Date: 06-23-2025
Last Update Date: 03-31-2026
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A mental health counselor like Olivia Crosby-gagnier provides treatment to individuals, families, couples, and groups for mental and emotional health issues and relationship problems. Mental health counselors treat clients with a variety of conditions, including anxiety, depression, grief, low self-esteem, stress, and suicidal impulses.

Location Map

Specialty - Primary Taxonomy

The NPI enumerator requires providers to submit at least one taxonomy code. A taxonomy code is a unique 10-character code that describes the healthcare provider type, classification, and the area of specialization. There could be only one primary taxonomy code per NPI record. For individual NPIs the license data is associated to the taxonomy code.

Classification: Counselor Mental Health
Taxonomy Code: 101YM0800X
Type: Behavioral Health & Social Service Providers

NPI NPI Number Validation

How NPI Validation Works

The NPI validation process uses the ISO-standard Luhn algorithm, a mathematical "handshake", to ensure that a provider's 10-digit ID is authentic and free of common typing errors.

To verify the NPI 1578450599, we treat the final digit (9) as the Check Digit—the target answer we need to reach. The process begins by taking the first nine digits and adding a constant value of 24, which accounts for the "80840" prefix required for all U.S. health identifiers. We then double every other digit starting from the right and sum the individual digits of those results together. For this specific NPI, that total comes to 71. The final step is to find the difference between that total and the next multiple of ten (80 - 71 = 9).

Digit-by-digit view

Use the first nine digits for the calculation. Starting from the right, double every other digit. The last digit is the check digit and is not part of the calculation.

Pos 1

Doubled → 2

Pos 2

Unchanged

Pos 3

Doubled → 14 → 1 + 4

Pos 4

Unchanged

Pos 5

Doubled → 8

Pos 6

Unchanged

Pos 7

Doubled → 0

Pos 8

Unchanged

Pos 9

Doubled → 18 → 1 + 8

Check

Target digit

Regular digit Doubled digit Check digit

Step 1: Double every other digit from the right

Starting with the rightmost digit of the first nine digits, double every other value. If doubling creates a two-digit number, add those digits together.

1 → 2 7 → 14 → 5 4 → 8 0 → 0 9 → 18 → 9

Step 2: Add all digits plus the NPI constant

Add the transformed values, the unchanged digits, and the constant 24.

2 + 5 + 1 + 4 + 8 + 8 + 5 + 0 + 5 + 1 + 8 + 24 = 71

Step 3: Find the amount needed to reach the next multiple of 10

The next multiple of ten after 71 is 80. The difference is the calculated check digit.

80 - 71 = 9

This NPI is valid

The calculated check digit is 9, which matches the last digit of 1578450599.