What actually counts as a peptide? The definition seems to cover everything

I have read What Peptides Actually Are twice and I think I am more confused than when I started, because the definition is so wide it seems useless.

A short chain of amino acids. Fine. But that means insulin is a peptide, semaglutide is a peptide, and so is the grey powder somebody is selling in a vial with no label. Those are obviously not the same kind of thing. So what is the word actually doing?

You have got it exactly right, and the confusion is the useful part. The word is doing almost nothing. It is a structural description — chain of amino acids, shorter than a protein, where the boundary is a convention rather than a fact — and it tells you nothing at all about whether something works, whether it is safe, or whether it is legal.

The thing people do with it is smuggle in the connotation. "Peptide" sounds biological, endogenous, gentle. Your body makes peptides, so a peptide must be natural, so it must be safe. Every step of that is wrong. Botulinum toxin is a protein your body did not make and will not thank you for.

The honest way to read it: "peptide" tells you what shape the molecule is. Everything you actually want to know is a separate question, asked per compound.

Adding the bit that made it click for me.

Ask what the word is being used instead of. When a pharmacy says peptide it is saying "this class of drug has delivery problems, it will be an injection". When a marketplace says peptide it is very often saying "this is not an approved medicine and I would rather not say the word unapproved".

Same word, two completely different jobs.

That is the answer I needed, thanks both. So the category is real chemically and near-meaningless commercially.

Follow-up then: is there a shorthand for the distinction I actually care about, which is "has this been tested in humans"?

There is, and it is the reason every compound page here carries two separate labels rather than one.

status — what the regulators have done. approved, off-label, research, cosmetic.

evidence — what the studies show, independent of that. strong, mixed, early, none.

They come apart more often than you would think. Tesamorelin is approved with strong evidence. Methylene blue is an approved drug with mixed evidence for what people actually buy it for. BPC-157 is research status with evidence: none, which on this site means exactly one thing: no completed human trial. Not "early", not "promising". None.

The index at /peptides shows both on every card. If you sort by evidence you get a much shorter list than the marketing would suggest, which is rather the point.

And it is worth staring at how short that list is. Of the thirty-four compounds documented on the blog, a handful carry strong and most of those are approved obesity or hormone drugs that went through phase 3 like any other medicine.

The interesting ones, the ones with the forums and the followings, are almost all none. That is not a coincidence and it is not a conspiracy. Compounds with completed trials get prescribed. Compounds without them get sold in vials.