Who is affected by the Category 1 vs 2 peptide framework

The FDA's peptide compounding classification system organizes bulk drug substances — the raw pharmaceutical ingredients used to make compounded preparations — into two categories. The classification determines whether a substance can be used in 503A compounding pharmacies, and under what conditions. It affects patients, prescribers, pharmacies, and telehealth platforms in different ways.

What is the difference between Category 1 and Category 2 peptides

The FDA's 503A bulk drug substance framework divides substances into three evaluation buckets:

• Category 1 substances have been nominated, reviewed, and placed on the 503A Bulks List — meaning they are eligible for use in compounded preparations under federal policy.
• Category 2 substances were nominated but reviewed and determined NOT to be appropriate for compounding — generally because they present safety concerns, because an FDA-approved drug already covers the same clinical need, or because the substance lacks sufficient clinical evidence.
• Substances still under review occupy a third, pending status.

The key practical distinction: a Category 1 substance can be used by a licensed 503A pharmacy to fill a valid patient prescription. A Category 2 substance cannot, under current federal policy.

Who does the peptide Category 2 classification affect

The classification affects four groups:

Patients who were prescribed or interested in a Category 2 peptide lose access through licensed 503A compounding pharmacies. They may have ongoing clinical relationships that need to be restructured around available alternatives.

Prescribing clinicians must work within the available substance list. For substances on Category 2, prescribing compounded versions is not supported by standard pharmacy channels.

Compounding pharmacies are legally prohibited from using Category 2 substances in preparations for individual patients. Continued use would expose them to regulatory and legal risk.

Telehealth platforms that had built protocols around Category 2 substances must revise their formularies or pause those protocols. The FDA issued over 30 warning letters to telehealth providers in 2026 related to compounding practices.

Which peptides are Category 1 and available from compounding pharmacies

The Category 1 list has evolved through FDA rulemaking and advisory committee review. The PCAC — Pharmacy Compounding Advisory Committee — a federal advisory body — reviews nominations and makes recommendations. Active clinical research is tracked at ClinicalTrials.gov.

Several peptides were reclassified to Category 1 in 2025 and 2026 following PCAC review. Others remain on Category 2 after safety or clinical necessity reviews found insufficient evidence to support compounding access. The list is not static — it continues to evolve through the nomination and review process.

For more on what changed in 2026, see the April 2026 reclassification explained, which 12 peptides were removed from FDA restriction, and how the PCAC advisory committee works. The broader 2026 peptide regulatory landscape provides full context. For prescriber context, see what off-label prescribing means.

Frequently asked questions

What is the difference between Category 1 and Category 2 peptides? Category 1 peptides are approved for use in 503A compounding pharmacies under federal policy. Category 2 peptides were reviewed and determined not appropriate for compounding — typically due to safety concerns or the availability of an FDA-approved equivalent.

Who does the peptide Category 2 classification affect? Patients, prescribers, compounding pharmacies, and telehealth platforms are all affected. Patients lose access through licensed channels; pharmacies cannot use these substances; telehealth platforms must revise protocols.

Which peptides are Category 1 and available from compounding pharmacies? The Category 1 list is maintained by the FDA and changes over time through the PCAC review process. Several peptides were reclassified to Category 1 in 2025–2026 following advisory committee review.

What is the PCAC? The PCAC — Pharmacy Compounding Advisory Committee — is the FDA's federal advisory body that reviews bulk drug substance nominations and makes recommendations on Category 1 eligibility. It meets periodically and its decisions are published publicly.

This article is educational and is not medical advice. Compounded medications are not FDA-approved. Clinical outcomes depend on individual factors and require physician evaluation. Results vary. Halftime Health is launching soon — join the waitlist to get updates.