Understanding GLN: The Complete Guide to Global Location Numbers in Pharmaceutical Supply Chain

Introduction: Why Location Identification Matters

In the complex world of pharmaceutical supply chain management, knowing what product you have is only half the battle—you also need to know where it came from, where it’s going, and who handled it along the way. This is where the Global Location Number (GLN) becomes indispensable.

As the pharmaceutical industry fully implements the Drug Supply Chain Security Act (DSCSA) requirements, GLNs have evolved from useful identifiers to mission-critical data elements. They serve as the digital addresses that enable traceability, ensure compliance, and maintain the integrity of every transaction in the drug distribution network.

Whether you’re a manufacturer shipping products to distributors, a wholesaler managing inventory across multiple facilities, or a dispenser verifying incoming shipments, understanding GLN is essential for operational success and regulatory compliance.

What Is a GLN?

A Global Location Number (GLN) is a unique 13-digit identifier assigned by GS1 that identifies any physical, functional, or legal location within a supply chain. Unlike product identifiers such as GTINs that tell you what something is, GLNs tell you where something is or who is involved in a transaction.

Think of a GLN as a digital address—just as your home address uniquely identifies where you live, a GLN uniquely identifies a specific facility, warehouse, office, or even a specific department within a larger organization. This standardization ensures that when trading partners exchange information, everyone is referring to the same location without ambiguity.

The Anatomy of a GLN

Understanding the structure of a GLN helps clarify how these identifiers function across the supply chain:

GS1 Company Prefix (Positions 1-7)

The first portion of a GLN is the GS1 Company Prefix, licensed from GS1 US or your local GS1 Member Organization. This prefix identifies the company or organization that owns the location. The length varies (typically 7-10 digits) based on how many locations and products a company needs to identify.

Location Reference (Variable Length)

The middle portion of the GLN is the location reference number assigned by the company to identify a specific location. The number of digits available depends on the length of your GS1 Company Prefix—the shorter your prefix, the more digits you have available for location references.

Check Digit (Position 13)

The final digit is a mathematical check digit calculated using a modulo-10 algorithm. This serves as a data integrity mechanism, allowing systems to instantly detect common data entry errors such as transposed digits or incorrect entries.

Types of Locations Identified by GLN

GLNs are remarkably versatile and can identify various types of locations:

Physical Locations

These are actual, tangible places where products are stored, manufactured, or handled:

• Manufacturing plants and production facilities

• Distribution centers and warehouses

• Pharmacy locations and hospital pharmacies

• Wholesale distributor facilities

• Contract manufacturing organizations (CMOs)

• Third-party logistics providers (3PLs)

Functional Locations

These represent specific functions or departments within a larger entity:

• Accounts payable departments

• Quality assurance offices

• Returns processing centers

• Customer service operations

• Specific loading docks within a larger warehouse

Legal Entities

GLNs can also identify legal entities for contractual or ownership purposes:

• Parent companies

• Subsidiaries

• Divisional headquarters

• Trading partner legal entities

GLN vs. SGLN: Understanding the Distinction

One common source of confusion is the difference between GLN and SGLN (Serialized Global Location Number). While they sound similar and serve related purposes, they serve distinct functions in serialization and traceability systems.

The GLN

A standard GLN is a 13-digit identifier used primarily for master data management and business transactions. When you see a GLN in everyday supply chain operations—on shipping documents, in purchase orders, or in master data exchanges—it’s typically the 13-digit version.

The SGLN

The SGLN is an extended version used specifically within Electronic Product Code Information Services (EPCIS) and Radio Frequency Identification (RFID) systems. The SGLN extends the GLN by adding a serial number or extension component, creating a unique identifier for a specific instance of a location or a specific read point.

SGLN Structure

An SGLN follows the EPC (Electronic Product Code) URI format and typically looks like this:

urn:epc:id:sgln:0614141.12345.400

Breaking this down:

• urn: epc: id: sgln – The EPC identifier indicating this is an SGLN

• 0614141 – The GS1 Company Prefix

• 12345 – The location reference

• 400 – The extension component (serial number or read point identifier)

The extension component is what transforms a GLN into an SGLN. This allows companies to identify not just the facility, but specific points within that facility—such as individual dock doors, specific production lines, or particular scanning stations.

When to Use Each

GLN’s Critical Role in DSCSA Compliance

The Drug Supply Chain Security Act has elevated GLN from a recommended best practice to a regulatory requirement. Understanding how GLN fits into DSCSA compliance is essential for all trading partners.

Transaction Information Requirements

Under DSCSA, every change of ownership transaction must include Transaction Information (TI) containing 11 data elements. GLN appears directly and indirectly in multiple elements:

• The business name and address of the seller – Often identified by the seller’s GLN

• The business name and address of the purchaser – Often identified by the purchaser’s GLN

• The business name and address from whom the seller directly received the product – Tracked via GLN

EPCIS Data Exchange

The FDA recommends GS1 EPCIS as the standard for electronic data exchange under DSCSA. EPCIS events require SGLNs to identify:

• Read points – Where events occurred (scanning stations, dock doors)

• Business locations – Where products are stored or handled

• Trading partners – Who sent and received products

In an EPCIS event, you might see SGLNs identifying that a product was commissioned at a specific manufacturing line (read point) within a specific facility (business location), then shipped from a particular dock door (read point) at the distribution center.

Authorized Trading Partner Verification

GLNs play a crucial role in verifying that you’re conducting business with authorized trading partners. When systems check ATP status, they often use GLNs to identify the specific locations involved in transactions, ensuring that both the corporate entity and the specific facility are properly licensed.

GLN in Master Data Management

Effective DSCSA compliance requires accurate master data exchange, and GLN management is a cornerstone of this process. Poor GLN management is one of the leading causes of data exchange failures and supply chain disruptions.

The Master Data Challenge

When a manufacturer sends an EPCIS file to a distributor, both parties must have consistent master data about each other’s GLNs. If the manufacturer uses a GLN that the distributor doesn’t recognize in their system, the transaction will fail, potentially causing:

• Shipment quarantine at receiving

• Delayed payment processing

• Compliance audit failures

• Supply chain disruptions

Best Practices for GLN Master Data

Centralize GLN Management

Designate specific individuals or teams to own GLN management within your organization. This ensures consistency in how GLNs are assigned, communicated, and maintained.

Implement Change Control Processes

Treat GLN additions and changes with the same rigor as document control or validation processes. When new GLNs are created or existing ones modified, follow a formal change control procedure that includes:

• Documentation of the change

• Review and approval by appropriate stakeholders

• Communication to all affected trading partners

• Updates to internal systems

• Verification that trading partners have processed the change

Proactive Communication

Don’t wait for trading partners to discover GLN issues during transaction processing. When establishing new trading relationships or modifying existing ones, proactively communicate GLN information before any product moves.

Cross-Reference Validation

Implement processes to ensure a single physical location maps to a single GLN. Multiple GLNs for the same location create confusion and data integrity issues.

DSCSA-Specific Contact Information

Maintain dedicated email addresses or contact points for DSCSA-related master data communications. This ensures that GLN updates reach the right people promptly, rather than getting lost in general business correspondence.

Common GLN Issues and How to Avoid Them

Even with careful management, GLN-related issues are common in pharmaceutical supply chains. Understanding these challenges helps prevent them.

Format Errors

One of the most frequent problems is incorrect GLN formatting. Common errors include:

• Omitting the check digit or using an incorrect one

• Including hyphens or spaces within the number

• Using 12 digits instead of 13

• Confusing GLN with other identifiers like DUNS numbers

Prevention: Implement system validation that checks GLN format and check digit accuracy before accepting data into your systems.

Missing Master Data

When a trading partner sends a file containing a GLN you don’t have in your system, automatic processing will fail. This often happens when:

• A manufacturer opens a new distribution center

• A contract manufacturing organization (CMO) begins production

• A company acquires another business with different GLNs

Prevention: Establish processes to review and update master data regularly. When onboarding new trading partners or establishing new locations, exchange GLN information before the first shipment.

Individually Licensed GLNs

Some companies obtain individually licensed GLNs directly from GS1 rather than using a company prefix. These GLNs may not be recognized by systems expecting GLNs derived from company prefixes.

Prevention: Ensure your systems can handle both prefix-derived and individually licensed GLNs. When receiving master data, verify which type of GLN your trading partner is using.

CMO and 3PL GLN Confusion

In contract manufacturing and third-party logistics arrangements, there’s often confusion about which GLN should appear in transaction data—the CMO/3PL’s GLN or the brand owner’s GLN.

Prevention: Establish clear contractual agreements about GLN usage in serialization data. Generally, the brand owner’s GLN should appear as the source of product, even when manufactured at a CMO facility. The CMO’s GLN may appear as a read point but should not replace the brand owner’s GLN in ownership transactions.

Outdated GLN Information

GLNs that were accurate at one time may become outdated due to facility closures, relocations, or business reorganizations. Using outdated GLNs causes data mismatches and compliance issues.

Prevention: Conduct periodic GLN audits and maintain open communication channels with trading partners about GLN changes. When receiving files with unexpected GLNs, investigate rather than simply rejecting.

Implementing GLN: A Practical Guide

For organizations establishing or refining their GLN infrastructure, here’s a practical implementation roadmap:

Step 1: Assess Your GLN Needs

Conduct a comprehensive assessment of all locations that need GLNs:

• Physical facilities: Manufacturing plants, warehouses, distribution centers, office locations

• Functional locations: Specific departments, processing areas, quality labs

• Trading partner considerations: Which locations will trading partners need to identify?

Step 2: License Your GS1 Company Prefix

If you don’t already have a GS1 Company Prefix, apply through GS1 US (or your local GS1 Member Organization). Consider:

• How many locations you need to identify now and in the future

• How many product GTINs you’ll also need (the same prefix serves both purposes)

• Whether a shorter prefix (more capacity) is worth the additional cost

Step 3: Develop Your GLN Assignment Scheme

Create a logical system for assigning location reference numbers:

• Sequential assignment: Simple but doesn’t convey information

• Hierarchical assignment: Location references encode facility type, region, or other attributes

• Functional assignment: Different ranges for different location types

Document your assignment logic for future reference and training.

Step 4: Calculate Check Digits

Use the GS1 check digit calculator (available on the GS1 US website) to generate valid check digits for each GLN. Ensure your systems can also calculate and verify check digits automatically.

Step 5: Implement Internal Systems

Update your ERP, WMS, serialization, and other operational systems to store and process GLNs:

• Add GLN fields to location master data

• Implement validation rules for GLN format and check digits

• Configure systems to include GLNs in EPCIS and other transaction data

Step 6: Exchange Master Data with Trading Partners

Establish processes for sharing GLN information with trading partners:

• Include GLNs in new trading partner onboarding

• Participate in industry master data services like HDA Origin

• Use GS1 Data Hub or similar platforms for data sharing

• Establish direct data exchange relationships with key partners

Step 7: Translate to SGLN for EPCIS

If you’re implementing EPCIS for DSCSA serialization, develop processes to translate your 13-digit GLNs into SGLN format:

• Determine your extension component scheme for read points

• Configure EPCIS systems to generate proper SGLN URIs

• Test SGLN generation and validation with trading partners

Step 8: Train Your Team

Ensure all relevant personnel understand GLN concepts and processes:

• Supply chain operations staff

• IT and system administrators

• Quality assurance and compliance personnel

• Customer service and trading partner liaison teams

Step 9: Monitor and Maintain

Establish ongoing processes for GLN management:

• Regular audits of GLN data accuracy

• Change control procedures for new or modified GLNs

• Communication protocols for GLN updates

• Periodic validation with trading partner systems

GLN Beyond DSCSA: Broader Supply Chain Applications

While DSCSA has made GLN essential for pharmaceutical companies, the benefits extend far beyond regulatory compliance:

Enhanced Traceability

GLNs enable precise tracking of products throughout the supply chain. When combined with GTINs and serial numbers, you can trace exactly which products were at which locations at what times—a capability invaluable for recalls, investigations, and quality management.

Improved Efficiency

Standardized location identification reduces errors in shipping, receiving, and inventory management. Warehouse systems can automatically route products to correct locations, and discrepancies are flagged immediately rather than discovered days later.

Better Analytics

With consistent location identifiers, you can analyze supply chain performance with greater precision: measuring dock-to-stock times by facility, comparing inventory accuracy across locations, or identifying the most efficient distribution paths.

Global Interoperability

GLN is a global standard recognized by trading partners worldwide. Whether you’re shipping domestically or internationally, GLN provides a common language for location identification that transcends borders and business systems.

Future-Proofing

As supply chain digitization accelerates, GLN provides the foundation for emerging technologies:

• Blockchain implementations for enhanced traceability

• Internet of Things (IoT) device identification

• Artificial intelligence and machine learning applications requiring clean location data

• Advanced analytics and digital twin modeling

Conclusion: Mastering GLN for Supply Chain Success

The Global Location Number has become an indispensable tool in modern pharmaceutical supply chain management. Under DSCSA and beyond, GLN enables the precise location identification necessary for transaction verification, regulatory compliance, and operational efficiency.

Understanding the distinction between GLN and SGLN, implementing robust master data management processes, and avoiding common pitfalls will position your organization for supply chain success. As the industry continues to evolve toward greater digitization and traceability, the foundation you build with proper GLN implementation today will support the innovations of tomorrow.

Whether you’re just beginning your DSCSA compliance journey or refining existing processes, treating GLN management as a strategic priority rather than an administrative afterthought will yield dividends in reduced exceptions, improved partner relationships, and enhanced supply chain resilience.

The pharmaceutical supply chain of the future runs on data—and GLN is the address system that makes that data meaningful.