---
title: "FDA Category 1, 2 and 3 Bulk Drug Substances Explained"
description: "FDA's Category 1, 2 and 3 decide which nominated bulk ingredients compounders may use. What each category means, and how Cuvo Health tracks them."
canonical: "https://cuvo.co/glossary/bulk-drug-substance-categories"
last-updated: "Oct 26, 2026"
---
**Definition:** FDA's bulk drug substance categories sort the ingredients nominated for its 503A and 503B bulks lists while FDA evaluates them: Category 1 may be used under FDA's interim policy, Category 2 raises significant safety risks, and Category 3 was nominated without enough support.

# What are FDA's bulk drug substance categories?

For a nominated ingredient that meets none of the statute's three tests, whether a pharmacy may compound with it is answered by an FDA interim policy with three categories. The categories explain why some peptides can be prescribed and compounded and others cannot. Cuvo Health tracks them for the brand, and its peptide program is limited to compoundable, provider-prescribed options.

Published Oct 26, 2026. Facts reviewed Oct 26, 2026.

FDA's bulk drug substance categories are the three groups FDA uses to sort active ingredients nominated for its 503A and 503B bulks lists while it evaluates them. Under section 503A, a pharmacy may compound from a bulk substance only if it meets a USP or NF monograph, is a component of an FDA-approved drug, or appears on the 503A bulks list, which FDA builds by regulation. Category 1 substances may be used under FDA's interim policy, Category 2 substances raise significant safety risks, and Category 3 substances lack enough supporting information. On Cuvo Health, the categories are tracked for the brand, and the peptide program is limited to compoundable, provider-prescribed options filled by licensed partner pharmacies.

**At a glance**
- Category 1: Nominated with enough support; FDA does not intend to act if its interim policy's conditions are met
- Category 2: Significant safety risks identified; outside the interim policy
- Category 3: Nominated without enough support; outside the interim policy; may be re-nominated
- Two sets: Separate categories for the 503A and 503B lists; a substance can sit in either or both
- Cutoff: FDA does not intend to categorize substances nominated on or after January 7, 2025
- On Cuvo: Categories tracked for the brand; peptides limited to compoundable, provider-prescribed options

**Where a nominated bulk ingredient can stand under section 503A**

| Status | What FDA says it means | Compounding from bulk |
| --- | --- | --- |
| **503A bulks list** | Placed on the list by final regulation | Allowed, with every other 503A condition |
| **Category 1** | May be eligible for the list; sufficient support to evaluate | FDA does not intend to act if the guidance conditions are met |
| **Category 2** | Significant safety risks pending further evaluation | FDA would consider action under its general enforcement policies |
| **Category 3** | Insufficient support to evaluate | FDA would consider action under its general enforcement policies |
| **Withdrawn or nominated since January 7, 2025** | Outside the categories | Only if a monograph or approved-drug test is met |

## 01. Why do the categories matter for a telehealth brand?

They decide which compounded preparations can reach a patient at all. A product page, an influencer script or a menu that promises a substance outside the lawful tests promises something no licensed pharmacy should fill. FDA publishes the safety risks it identified for each Category 2 substance, so a brand whose offer depends on one is building on a substance FDA has flagged.

On Cuvo, no fixed peptide catalogue is published: a provider licensed in the patient's state decides whether any treatment is appropriate, and the order routes to a licensed partner pharmacy operating within the current rules for the molecule.

## 02. How does a substance get onto a bulks list?

For 503A, by notice-and-comment rulemaking after FDA consults its Pharmacy Compounding Advisory Committee, as 21 U.S.C. 353a(c) requires. FDA's February 2019 final rule placed six substances on the list; a September 2019 proposed rule has not been finalized. For 503B, FDA proposes and designates substances by Federal Register notice; on May 1, 2026 it proposed not to include semaglutide or tirzepatide on the 503B bulks list (91 FR 23431). An advisory committee's advice does not by itself place a substance on either list.

## 03. What does Category 2 mean for peptides?

Several peptides have been placed in Category 2, which means FDA identified significant safety risks and keeps them outside the Category 1 forbearance. FDA's Category 2 page, current as of April 22, 2026, also keeps a section of substances whose nominations were withdrawn, each still listed with its safety risks; withdrawal does not by itself place a substance in Category 1. Cuvo's 2026 peptide rules guide, linked below, dates each change. This is general information, not legal advice.

## Frequently asked questions

**Q: What are Category 2 peptides?**

A: They are peptides FDA has placed in Category 2 of its interim bulk substance policy because it identified significant safety risks, so they fall outside the policy's forbearance. On Cuvo, the peptide program is limited to compoundable, provider-prescribed options, and none is promised to a patient in advance.

**Q: What is the 503A bulks list?**

A: It is FDA's regulation listing bulk substances a 503A pharmacy may compound with when no USP or NF monograph exists and the substance is not part of an FDA-approved drug. On Cuvo, providers and licensed partner pharmacies work within the list and the interim categories as they stand.

**Q: What is the difference between Category 1 and Category 2?**

A: Category 1 substances may be compounded under FDA's interim policy while FDA evaluates them, and Category 2 substances raise significant safety risks and are outside that policy. On Cuvo, what current rules permit is tracked for the brand, and each prescription routes only to a licensed pharmacy operating inside those rules.

**Q: Can a pharmacy compound a Category 2 substance?**

A: FDA says it would consider taking action against a compounder that uses one under its general enforcement policies, so a Category 2 substance is not a lawful basis for a compounded program. On Cuvo Health, the peptide program is limited to compoundable, provider-prescribed options.

**Q: Does a telehealth brand need to track FDA's bulk categories?**

A: It needs a partner that does, because the categories change and a brand's product claims must follow them. Cuvo Health tracks what current rules permit and routes each prescription only to a licensed pharmacy operating inside those rules, so a program changes only when the rules do.

**Related pages**

- [FDA peptide compounding rules in 2026](/blog/fda-peptide-compounding-rules-2026): Every 2026 change, dated from primary sources
- [503A compounding pharmacy](/glossary/503a-pharmacy): The three bulk-substance tests in context
- [503B outsourcing facility](/glossary/503b-outsourcing-facility): The 503B bulks list and the shortage pathway
- [Research use only (RUO) products](/glossary/research-use-only): Why a lab label is not a compounding route
- [Peptide programs on Cuvo](/solutions/peptides): Provider review and licensed pharmacy routing
- [Telehealth glossary](/glossary): Every term a telehealth founder meets

Canonical page: https://cuvo.co/glossary/bulk-drug-substance-categories