How to evaluate a research peptide supplier.
Most supplier websites look the same. The differences that matter are verifiable. Use this checklist on anyone, including us.
1. Do they prove purity, or just claim it?
Anyone can print "99% pure" on a label. The question is whether an independent laboratory verified that number with HPLC and confirmed identity with mass spectrometry — when outside labs have measured peptide vials sold online, the measured purity has diverged sharply from the label claim. Ask for the Certificate of Analysis for the exact lot you would receive. A supplier who hesitates has answered your question — hesitation over lot-level documentation is one of the clearest red flags in research peptide sourcing.
2. Is the compliance language honest?
Legitimate research suppliers state plainly that products are for laboratory research use only and not for human consumption, and they avoid medical claims entirely. Sites that promise outcomes or blur that line are signaling how they will handle everything else.
3. How is the material handled?
Lyophilized peptides are stable when stored correctly, but storage and transit conditions matter, and they matter more the longer the route — one of the reasons domestic and overseas sourcing are worth weighing separately. Look for suppliers who describe cold storage and protective shipping rather than treating vials like a t-shirt order.
4. Does anyone answer?
Send a question before your first order: about a COA, a lot number, anything. The speed and quality of that reply is the best preview you will get of what happens if an order ever has a problem.
5. Are policies published?
Shipping, returns, privacy, and terms should be public and readable before checkout, not discovered after a dispute.
The pattern behind the checklist
Every item above is the same test: does the supplier show their work? Documentation, testing, policies, and responsiveness are hard to fake at the same time. Marketing is easy to fake alone. The documentation only earns its keep once it is checked, which is why the verification steps that precede an experiment begin with matching the certificate to the lot in hand.
For the full guide, with each item expanded and the reasoning behind it, read how to evaluate a research peptide supplier on the Research Blog.
Steadfast publishes its standard, its Certificates of Analysis, and its policies, and answers every message. Hold us to it.