What should I look for in a peptide vendor (quick checklist)?

No single signal proves quality, but transparency is the thing that separates vendors worth considering from ones that are not.

Trust signals worth checking

• Third-party COAs (HPLC/MS) from a named independent laboratory — not an in-house document with no lab identified.
• Lot and batch identifiers that actually match the vial you received.
• Transparent contact information: a real address and a working support channel.
• Consistent trading history and reviews over time rather than a burst of recent ones.
• Clear shipping, storage and returns policies, including whether cold-chain handling is used.

Red flags on certificates specifically

• A COA with no lot number, or a lot number that does not match the vial.
• The same certificate reused across multiple products or batches — check the dates and lot fields.
• No testing laboratory named, or a laboratory that does not appear to exist.
• Purity claimed without a chromatogram. A number on its own is an assertion; the trace is the evidence.

On price

Pricing far below the market is a signal, not a bargain. Synthesis has a floor cost, and the usual explanations for beating it are underfilled vials, lower net peptide content, or material that is not what the label says.

Compare listings on price per mg via the vendor comparison, and see how rankings work — placement cannot be bought. Research use only. Not medical advice.