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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:
The UNII may be found in:
Questions about the UNII should be directed to fda-srs@fda.hhs.gov
FDA Substance Registration System User's Guide Version 5c
Released UNIIs and their Preferred Terms
Inactive Ingredient Query Application Frequently Asked Questions Regarding the UNII