Peptides: what is proven, and what is sold
A handful of authorised medicines, a very large grey market, and a literature that is thin, short and mostly in animals.
Key takeaways
- Peptide medicines such as insulin and GLP-1 agonists are authorised; most online peptides are not.
- 'Research use only' is a legal disclaimer, not a quality or safety designation.
- The evidence base for grey market peptides is mostly animal studies and preprints.
- Even if a peptide had a plausible rationale, unregulated vials cannot be assumed to contain what the label says.
Peptide is a chemical description, not a category of treatment, and this causes more confusion than any other word in the field. Insulin is a peptide. So are the GLP-1 receptor agonists, teriparatide for osteoporosis, octreotide, desmopressin and a number of other authorised medicines with dossiers, defined indications and pharmacovigilance behind them. These went through the same regulatory machinery as any other drug.
The market that has grown up under the same word is a different thing entirely. The compounds circulating online for tissue repair, tanning, growth hormone release, immune modulation or general enhancement are, with few exceptions, not authorised as medicines anywhere in the EU. Several appear on the World Anti-Doping Agency prohibited list, which is a statement about competitive sport rather than a safety assessment, but it does mark them out as biologically active enough to be worth banning. The research base is usually a small animal literature, a handful of short human studies with surrogate endpoints, or preprints, and it thins out sharply the moment you look for anything long enough to detect harm.
Research use only, printed on a vial, is not a quality designation. It is a legal position: the seller is stating the product is not for human use, which removes it from the medicines regime and transfers the entire risk to whoever ignores the label. It says nothing about identity, purity, sterility or dose accuracy, and it is precisely the phrase that allows an unregulated supply chain to operate in the open.
Two problems are being conflated and are worth separating. The first is that for most of these compounds the evidence does not support the claimed benefits in humans at all; the marketing is running decades ahead of the data. The second is that even for the few with a plausible rationale, nobody can tell you what is actually in an unregulated vial. Solving the second would not solve the first.
Notes and sources
Each regulatory statement in this article is set against the document it comes from, so you can read the original rather than our summary of it.
1. Peptide medicines require authorisation and are assessed for quality, safety and efficacy
2. Substances sold as research chemicals are not authorised for human use
3. Regulatory action on compounded and unapproved peptide products
4. Several peptides appear on the prohibited list in sport
