503A Category 1, 2 or 3? What Each Means in 2026

Summary. FDA sorts bulk drug substances nominated for the 503A bulks list into three categories while it reviews them, and the label decides how FDA approaches compounding with that substance in the meantime. According to FDA, a 503A compounder may use a bulk drug substance only if it complies with a USP or National Formulary monograph, is a component of an FDA-approved drug product, or appears on the 503A bulks list; it must also come from an FDA-registered establishment with a valid certificate of analysis. Category 1 covers nominated substances with sufficient supporting information that may be eligible for the list; FDA says it does not intend to take action against compounding with them if the conditions of its guidance are met. Category 2 covers substances that raise significant safety risks, and FDA says it would consider action under its general enforcement policies; the safety information is posted on FDA.gov. Category 3 covers nominations without enough supporting information; they can be nominated again, but they do not get the Category 1 policy. Our FDA Peptide Compounding Policy Tracker follows each step.

Research context (RUO). The categories are interim labels, not approvals. FDA says a Category 1 substance keeps that status until FDA decides whether to place it on the list, or until FDA moves it, for example over safety risks, and that it does not intend to categorise substances nominated on or after 7 January 2025. The list can change quickly: FDA's May 14, 2026 update records one substance taken out of Category 1 on 22 April 2026 after its nominations were withdrawn, then set to return after a nominator clarified on 5 May. The policy that the Department of Health and Human Services published on 30 October 2026 (FR Doc. 2026-22192) is a separate route: it is an HHS draft enforcement discretion policy for six peptide substances listed in its Appendix A, intended to apply until a final rule addresses each one. HHS says the policy is not binding, that it may revisit it if a safety signal or product quality issue arises, and that comments are open on regulations.gov until 13 November 2026, two weeks after publication. If the terms are new, our Academy chapter on basic terms explains them, and the COA page shows what a lot-level certificate contains. These rules concern compounding for patients, not research-grade material.

This summary is for research-community awareness only and is not legal advice. For research use only. Not for human or veterinary use.