What is the unique identifier for drugs?: Understanding the National Drug Code

October 10, 2025 •

4 min read

Every single prescription and over-the-counter (OTC) medication in the United States is assigned a distinct identifier to ensure safety and traceability. This unique identifier for drugs is the National Drug Code (NDC), a standard established by the U.S. Food and Drug Administration (FDA).

Quick Summary

The National Drug Code (NDC) is the primary U.S. identifier for human drugs, featuring a three-segment number to specify the labeler, product, and package size. The code is vital for medication management, billing, and ensuring safety in the supply chain. Other identifiers like RxNorm, UNII, and DEA numbers serve different functions within the healthcare system.

Key Points

National Drug Code (NDC): The NDC is the unique, three-segment identifier for all human drugs in the U.S., assigned by the FDA and manufacturers.
NDC Segments: The NDC's three parts specify the labeler (manufacturer), the product (strength, dosage), and the package size.
10-Digit vs. 11-Digit NDC: While 10-digit NDCs appear on packaging, an 11-digit version is required for billing by payers like CMS, necessitating a leading zero to be added to one of the segments.
RxNorm for Standardization: RxNorm is a system used to normalize drug names and concepts for electronic health records, aggregating multiple NDCs under a broader clinical concept.
UNII for Ingredients: The Unique Ingredient Identifier (UNII) is assigned by the FDA to identify the active ingredient's chemical structure.
DEA Number for Prescribers: A DEA number identifies a provider authorized to prescribe controlled substances, not the drug itself.

The National Drug Code (NDC): A Closer Look

The National Drug Code (NDC) is a universal product identifier for human drugs sold in the United States, appearing on all prescription and OTC medication packages. This standardized system allows for the precise tracking of drugs from the manufacturer to the patient and is essential for billing and supply chain management. The NDC number is a 10- or 11-digit code broken into three key segments.

The Three Segments of an NDC

The NDC is a three-part numerical code where each segment provides specific, detailed information about the medication.

Labeler Code: The first segment identifies the manufacturer, repackager, or distributor. This code is assigned by the FDA. A firm with a 5-digit labeler code must choose between a 4-digit product code and a 1-digit package code or a 3-digit product code and a 2-digit package code.
Product Code: The middle segment specifies the drug's active ingredient, dosage form (e.g., tablet, capsule), and strength. This part is assigned by the manufacturer.
Package Code: The final segment identifies the specific package size and type (e.g., a bottle of 100 tablets versus a bottle of 50 tablets). This, too, is assigned by the manufacturer.

For example, the NDC for a specific ibuprofen tablet might be 42681-0026-1. Here, 42681 is the labeler code, 0026 is the product code for the 200mg tablet, and 1 is the package code.

Understanding the 10- and 11-Digit NDC

One of the most common points of confusion regarding NDCs is the 10-digit versus 11-digit format. While the 10-digit NDC is printed on drug packaging, the Centers for Medicare & Medicaid Services (CMS) and other payers require an 11-digit, 5-4-2 format for billing purposes. To convert a 10-digit NDC to an 11-digit one, a leading zero is inserted into the segment that has fewer digits than its assigned standard format.

Example of Conversion:

A 10-digit NDC 1234-1234-12 becomes 01234-1234-12 (add zero to the labeler code).
A 10-digit NDC 12345-123-12 becomes 12345-0123-12 (add zero to the product code).
A 10-digit NDC 12345-1234-1 becomes 12345-1234-01 (add zero to the package code).

This standardization is critical for electronic health record (EHR) systems and billing software to correctly identify and process claims for dispensed medications.

Other Important Drug Identifiers

While the NDC is the most common product-level identifier in the U.S., other systems and codes serve different, but equally important, purposes within the healthcare ecosystem. These identifiers classify and standardize drugs based on ingredients, clinical concepts, and usage, not just the finished product.

Unique Ingredient Identifier (UNII): Generated by the FDA's Global Substance Registration System (GSRS), a UNII is a non-proprietary, unique, and unambiguous identifier for a substance's molecular structure or descriptive information. It is used to identify active ingredients in a drug product.
RxNorm: This standardized nomenclature, created by the National Library of Medicine (NLM), is used for clinical drug information. It normalizes the different names for identical medications, allowing EHRs and pharmacy systems to communicate unambiguously about drug concepts, rather than a specific product package. RxNorm aggregates multiple NDCs under a single concept.
Drug Enforcement Administration (DEA) Number: This number is assigned to healthcare providers who are authorized to prescribe controlled substances. It is not a drug identifier but an prescriber identifier.

Comparison of Major Drug Identifiers


Feature	NDC (National Drug Code)	RxNorm	UNII (Unique Ingredient Identifier)	DEA Number
Purpose	To identify a specific finished drug product and its package size.	To standardize clinical drug names and concepts for electronic health records.	To provide a unique, non-proprietary identifier for specific active ingredients.	To track and authenticate prescriptions for controlled substances.
Granularity	Highly specific: distinguishes between manufacturer, product, and package.	Aggregate: groups products with the same active ingredient, strength, and dosage form.	Ingredient-based: identifies the substance itself, not the finished product.	Prescriber-based: identifies the provider, not the drug.
Assigning Agency	FDA (labeler code) and drug manufacturer (product and package codes).	National Library of Medicine (NLM).	FDA's Global Substance Registration System (GSRS).	Drug Enforcement Administration (DEA).
Usage	Billing, inventory management, supply chain tracking.	Clinical decision support, drug information exchange.	Drug regulation and active ingredient identification.	Controlled substance prescribing.

The Critical Role of Drug Identifiers in Medication Safety

Accurate drug identification is fundamental to patient safety. Identifiers like the NDC help prevent medication errors by ensuring the correct drug, dosage, and package are dispensed. When healthcare professionals use EHRs, the standardized RxNorm names ensure clarity and reduce ambiguity, which can be critical during medication reconciliation. For example, if a patient is allergic to a certain active ingredient, the UNII can help trigger an alert, and an NDC mismatch during dispensing can prevent a wrong-drug error.

Furthermore, NDCs play a crucial role in public health monitoring. They enable agencies like the FDA to track drug recalls and monitor adverse events effectively. In the complex pharmaceutical supply chain, the Drug Supply Chain Security Act (DSCSA) mandates that manufacturers place unique identifiers on individual prescription drug packages, including the NDC, lot number, and expiration date. This creates a traceable record of a drug's journey, which is crucial for preventing counterfeit or illegitimate products from entering the market.

Conclusion

The National Drug Code is the backbone of drug identification in the United States, providing a specific, product-level identifier that is indispensable for labeling, tracking, and billing. While the NDC is highly granular, other identifiers like RxNorm and UNII serve to standardize drug concepts and ingredients for broader clinical and regulatory purposes. These systems work in concert to ensure medication safety, streamline supply chain operations, and provide clarity within the complex world of pharmacology. A correct and consistent understanding of these unique identifiers is vital for everyone involved in the dispensing and administration of medication.

Food and Drug Administration: National Drug Code Database Background Information

Frequently Asked Questions

The NDC is typically printed on the drug's packaging, usually near the barcode. For prescription drugs, it may also be on the pharmacy label.

An NDC is a product identifier that specifies the drug, manufacturer, and package size. A DEA number identifies a healthcare provider authorized to prescribe controlled substances, not the medication itself.

Payers like Medicare and Medicaid require an 11-digit NDC on claims for covered drugs to ensure accurate reimbursement. Incorrect or missing NDCs can lead to claim denials.

Yes, an NDC can change if the manufacturer, formulation, or package size is altered. Each specific product and package size from a manufacturer has a distinct NDC.

RxNorm groups various NDCs for identical drugs (same ingredient, strength, and dosage form) under a single standardized name, which is useful for clinical data exchange.

A UNII is a unique identifier assigned to a substance's molecular structure, meaning it identifies the specific active ingredient of a drug, not the finished product.

Yes, websites and drug databases often allow searching by NDC code to find information and images of a specific medication.