How to evaluate a peptide supplier
This page does not sell, rank, or endorse suppliers. It lists the checks and questions people commonly use to assess a source, so you can judge one yourself.
What to check
Third-party analytical testing
Look for HPLC purity and mass-spectrometry identity results from an independent lab, not an in-house claim. A result should name the lab, the method, and the batch.
Batch-specific certificate of analysis
A certificate of analysis should match the lot number printed on the vial. A single undated certificate reused across every product tells you nothing about what you received.
Labeling that matches the vial
Compound name, stated amount, lot number, and any statement of intended use should be legible and consistent. Mislabeled or unlabeled vials make every downstream calculation meaningless.
Storage and shipping handling
Ask how lyophilized material is stored and whether cold-chain shipping is used. Temperature history affects what actually arrives.
Regulatory status and claims
Many peptides are sold as research chemicals and are not approved for human use. Any supplier making therapeutic promises is making a claim they are not permitted to make.
Transparency and support
A verifiable business address, responsive support, a written return policy, and willingness to answer testing questions are the baseline, not extras.
Red flags
- Dosing advice or medical claims from the seller
- No lot numbers and no batch-level testing
- Certificates with no lab name, method, or date
- Prices far below every other supplier with no explanation
- Pressure tactics, disappearing storefronts, or crypto-only checkout with no support channel
Questions worth asking
- Which independent lab tested this batch, and can I see the report?
- What purity threshold do you reject a batch at?
- How is the product stored before shipping, and is it shipped cold?
- What is the lot number on the vial I would receive?
- What happens if the vial arrives damaged or unlabeled?
Once you know what you have, record it: the peptide calculator converts a vial into draw volume, and the research index shows what has actually been studied.