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Substance Registration System - Unique Ingredient Identifier (UNII)

The overall purpose of the joint FDA/USP Substance Registration System (SRS) is to support health information technology initiatives by generating unique ingredient identifiers (UNIIs) for substances in drugs, biologics, foods, and devices. The UNII is a non- proprietary, free, unique, unambiguous, non semantic, alphanumeric identifier based on a substance’s molecular structure and/or descriptive information.

The procedures and management of the SRS is provided by the SRS Board. The SRS Board includes experts from both FDA and USP. The SRS operating procedures defined by the SRS Board are detailed in the SRS Manual.

The UNII is:

• One of the core components of the United States Federal Medication Terminology.
• Used in the FDA's Structured Product Labeling
• Used to assist in the generation of the National Library of Medicine's (NLM's) RxNorm.
• A US government standard for drug ingredient and food allergen identifiers
• A component of the Environmental Protection Agency's Substance Registry System (future)

The UNII may be found in:

• NLM's Unified Medical Language System (UMLS)
• National Cancer Institutes Enterprise Vocabulary Service
• USP Dictionary of USAN and International Drug Names (future)
• FDA Data Standards Council website
• VA National Drug File Reference Terminology (NDF-RT)
• FDA Inactive Ingredient Query Application

Questions about the UNII should be directed to fda-srs@fda.hhs.gov

SRS Resources

FDA Substance Registration System User's Guide Version 5c

Released UNIIs and their Preferred Terms

Substance Registration System – Unique Ingredient Identifier (UNII) Presentation - CAPT. William A Hess, FDA

Inactive Ingredient Query Application Frequently Asked Questions Regarding the UNII

FDA Data Standards Council Home Page

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