Most peptide guides tell you what a compound is. Almost none tell you how to judge the people selling it — which, once you have decided what you want, is the only question left.
This is the checklist I use. It takes about ten minutes to run and it eliminates most of what is wrong with this market.
Not “COA available on request.” A real supplier publishes the COA for the batch you are buying, with the lab’s name on it. If you cannot see the document before you order, treat the purity number as marketing copy.
In-house means the seller graded their own homework. Look for an independent lab named on the certificate — and check that the lab exists.
“99%+” on its own means nothing. HPLC and mass spectrometry answer different questions; a serious COA names the method and shows the trace.
The number on the vial should match the number on the COA. This is the single easiest check to run and the one most often skipped.
Lyophilised material is stable at room temperature for shipping, but how it was stored before it shipped matters. A supplier who says nothing about storage has told you something.
Anything sold for laboratory research should say so plainly on the label and the site. A vendor blurring that line is taking a risk with their business, and with yours.
Packages go missing. A supplier with a written policy has thought about it; one without will improvise at your expense.
Send one question and time the reply. It is the cheapest possible test of what support looks like after they have your money.
Work top to bottom and stop at the first failure. In practice checks 1 and 4 — a visible COA and a batch number that matches the vial — remove most candidates before you reach the rest.
We do not recommend or partner with any peptide supplier. Use the checklist instead: third-party COAs that match your batch and lot, stated purity, clear research-use labeling, real support and proper cold-chain shipping.
The supplier checklist →Educational content only. Confirm the legal status where you live before ordering anything.