How the FDA categorizes peptides for 503A compounding
The sorting hat for compounded peptides — and the rules behind which one a peptide ends up in.
TL;DR
- The FDA sorts compounding-eligible bulk substances into Category 1 (compoundable) and Category 2 (not eligible for 503A compounding).
- The FDA assigns the categories. The Pharmacy Compounding Advisory Committee (PCAC) advises the FDA on which substances to add to the 503A bulks list, and the FDA makes the final decision.
- In 2023, the FDA moved several popular research peptides, including melanotan-2, to Category 2. FDA removed most of them from Category 2 in September 2024 or April 2026.
What it is
The Category 1 / Category 2 framework is how the FDA sorts bulk substances proposed for compounding under Section 503A of the Federal Food, Drug, and Cosmetic Act. The 503A bulks list is the public registry of which substances may be compounded by state-licensed 503A pharmacies. Category 1 substances are eligible while review continues or after a positive recommendation. Category 2 substances are flagged as posing significant safety risks or as having insufficient evidence to support a clinical need (FDA, 503A bulks).
How it works
Think of PCAC as a building permit office. Anyone may nominate a substance for the 503A list. The committee reviews the physicochemical profile, the historical use, the available safety data, and any safety signals. It then makes a non-binding recommendation. The FDA reviews the recommendation and publishes its decision in the Federal Register. A substance does not become "approved." It becomes eligible — or not eligible — to be compounded.
Who asks about it
People come to this topic after their physician explains that a peptide they read about online is "Category 2" and not currently available at the local 503A pharmacy. Many are surprised the FDA does not "approve" or "ban" peptides per se. The actual mechanism is narrower: it decides whether each substance is eligible to be compounded into patient-specific medications.
What the research says
The framework was clarified in the Drug Quality and Security Act (DQSA) of 2013 and has been applied to dozens of substances since. PCAC meetings publish meeting minutes and decision rationales. Category 2 decisions for several peptides cited insufficient human safety data — not evidence of harm (Federal Register, 2019 503B list as reference). FDA removed 12 peptides from Category 2 on April 22, 2026, after their nominations were withdrawn. In February 2026, HHS Secretary Robert F. Kennedy Jr. said in a podcast interview that FDA would soon make more peptides accessible. That was not a formal proposal; the formal step was FDA's April 2026 change to its category list.
What to know before considering it
Category status changes. A peptide that is Category 2 today may move to Category 1 after a Federal Register update. A peptide that is Category 1 today may move the other way if new safety signals emerge. Any access to a compounded peptide requires a licensed prescriber and a state-licensed 503A pharmacy. Cross-border or "research-use-only" peptides do not pass through this framework at all.
The Halftime POV
The category system is not a verdict on a peptide's value. It is a regulatory status that can change with new data. Patients are best served by physicians who know the current status, the current evidence, and the difference between the two.
Related reading:
- The 'banned overnight' myth: what actually happened to peptides in 2023
- How 503A pharmacies compound peptides from API to vial
FAQ
Q: How does the FDA categorize peptides for compounding? A: The FDA places nominated bulk substances into categories, including Category 1 (eligible for compounding under 503A while under evaluation) and Category 2 (significant safety risk or not eligible). The FDA publishes the category list. The FDA's Pharmacy Compounding Advisory Committee (PCAC) advises the FDA on whether to add a substance to the 503A bulks list. The committee is advisory, and the FDA makes the final decision.
Q: What is the difference between Category 1 and Category 2? A: Category 1 substances may be compounded under 503A while review is ongoing or after a positive recommendation. Category 2 substances are flagged for significant safety risk or insufficient evidence and are not eligible for 503A compounding.
Q: Which peptides became Category 2 in 2023? A: The FDA reclassified melanotan-2 and several other peptides to Category 2. The decision was based on insufficient human safety data, not on evidence of harm. FDA removed some of these peptides from Category 2 on September 27, 2024, and others, including melanotan-2, on April 22, 2026, after their nominations were withdrawn. Of the 19 peptides FDA added to Category 2 in 2023, only ibutamoren (MK-677) and kisspeptin-10 remain in Category 2 as of September 14, 2026.
Q: Is Category 2 status permanent? A: No. FDA removed 5 of the peptides it added in 2023 from Category 2 on September 27, 2024, and 12 more on April 22, 2026, after their nominations were withdrawn. In February 2026, HHS Secretary Robert F. Kennedy Jr. said in a podcast interview that FDA would soon make more peptides accessible. That was not a formal proposal; the formal step was FDA's April 2026 change to its category list. At its July 23–24, 2026 meeting, FDA's Pharmacy Compounding Advisory Committee voted to recommend adding six of these peptides to the Section 503A bulk drug substances list. It voted against recommending one other. The committee is advisory. As of September 14, 2026, FDA has not made a final decision.
Disclaimer
Several peptides discussed in this article, including melanotan-2, were previously in FDA's Category 2. FDA removed them from Category 2 (September 2024 or April 2026, depending on the peptide). As of September 14, 2026, they are not in any FDA 503A category and are not on the 503A bulks list. At its July 23–24, 2026 meeting, FDA's Pharmacy Compounding Advisory Committee voted to recommend adding some of these peptides to the Section 503A bulk drug substances list. The committee is advisory, and formal addition to the list requires further FDA action. As of September 2026, FDA has not made a final decision. This article is educational and is not medical advice. Prescriptions are written only by independently licensed physicians, in states where they are licensed.
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Frequently asked questions
How does the FDA categorize peptides for compounding?
The FDA places nominated bulk substances into categories, including Category 1 (eligible for compounding under 503A while under evaluation) and Category 2 (significant safety risk or not eligible). The FDA publishes the category list. The FDA's Pharmacy Compounding Advisory Committee (PCAC) advises the FDA on whether to add a substance to the 503A bulks list. The committee is advisory, and the FDA makes the final decision.
What is the difference between Category 1 and Category 2?
Category 1 substances may be compounded under 503A while review is ongoing or after a positive recommendation. Category 2 substances are flagged for significant safety risk or insufficient evidence and are not eligible for 503A compounding.
Which peptides became Category 2 in 2023?
The FDA reclassified melanotan-2 and several other peptides to Category 2. The decision was based on insufficient human safety data, not on evidence of harm. FDA removed some of these peptides from Category 2 on September 27, 2024, and others, including melanotan-2, on April 22, 2026, after their nominations were withdrawn. Of the 19 peptides FDA added to Category 2 in 2023, only ibutamoren (MK-677) and kisspeptin-10 remain in Category 2 as of September 14, 2026.
Is Category 2 status permanent?
No. FDA removed 5 of the peptides it added in 2023 from Category 2 on September 27, 2024, and 12 more on April 22, 2026, after their nominations were withdrawn. In February 2026, HHS Secretary Robert F. Kennedy Jr. said in a podcast interview that FDA would soon make more peptides accessible. That was not a formal proposal; the formal step was FDA's April 2026 change to its category list. At its July 23–24, 2026 meeting, FDA's Pharmacy Compounding Advisory Committee voted to recommend adding six of these peptides to the Section 503A bulk drug substances list. It voted against recommending one other. The committee is advisory. As of September 14, 2026, FDA has not made a final decision.
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