Decide your scoring before anyone answers
Write down what a pass looks like before you contact the first supplier. If you decide afterwards, the supplier with the friendliest reply or the lowest price tends to win, whatever the paperwork says.
| Check | Pass | Fail |
|---|---|---|
| Lab reports | One report per batch, from a named independent lab, with a report key you can look up | The same report reused across batches, no lab name, or a PDF you cannot trace |
| Your own test | A sample you bought blind matches the claimed identity, purity and quantity | Any gap between the report and your own test |
| Lot numbers | Lot on the vial matches the lot on the report and the invoice | Missing or mismatched lots |
| Price sheet | Priced per vial with the amount per vial stated, so you can work out cost per milligram | Prices with no strength, or strengths that change between sheets |
| Communication | Straight answers in writing within a day or two | Pressure to pay fast, or answers that change |
The questions to ask every supplier
Send the same list to everyone, in writing, so the answers can be compared side by side.
- Do you make the material yourselves, or buy it from a manufacturer? If you buy it, from whom?
- Which independent lab tests each batch, and can I look the report up on the lab's own site?
- Is there one report per batch, and will the lot number on my vials match it?
- What is the amount per vial, and how much variation do you allow?
- What are your minimum order, lead time and payment terms for a first order and for repeat orders?
- How do you pack and ship, and who pays if a parcel is held or lost?
- What happens if my own test does not match your report?
The last question matters most. A supplier with a clear, written answer about replacements and refunds has usually been asked before and stood behind it.
Read the paperwork like a buyer would
Read the supplier's lab reports the way your own buyers will read yours. Check that the lab exists, that the report key opens the same document on the lab's site, that the test date is recent, and that the lot number matches what you are being offered. Our guide on how buyers verify a peptide COA walks through the ten-second version.
Watch for reports that look identical except for the date, purity figures that are the same to two decimal places across several batches, and reports that only cover purity without confirming identity. None of these prove fraud, but each one is a reason to test before you buy.
Test a sample yourself, blind
Order a small quantity as an ordinary customer, send one or more vials to an independent lab under a neutral label, and compare what comes back with the supplier's report. The lab does not need to know who the supplier is, and the supplier does not need to know which vials you tested.
- Test identity and purity at a minimum, and quantity per vial if the price depends on it.
- Record the lot number, the date received and the lab's report key together.
- If the numbers differ, ask the supplier to explain before you decide. Sometimes it is a labelling mistake. Sometimes it is the answer you needed.
Our guide to peptide testing labs compares the labs sellers use most, and peptide lab tests explained covers which tests to order.
Start small, then scale
Paper and one good sample earn a small first order, not volume. Place a first order you could afford to lose, test that batch too, and only raise quantities after two or three batches have matched their reports.
Keep at least two suppliers for anything you sell a lot of. When a supplier runs out, changes manufacturer or goes quiet, the second one keeps you in stock. Compare them fairly with the cost per milligram calculator, because a cheaper vial with less in it is not cheaper.
Warning signs that mean walk away
- They offer to describe the goods as something else on the shipping paperwork.
- They will not name the lab, or the lab cannot find the report.
- Every batch shows the same purity to the decimal.
- Payment details change mid-conversation, or you are asked to pay a different account than last time.
- They are happy to discuss how the products are used in people. A supplier who talks that way will put your business at risk too.
Doing it in Purity
Purity keeps every supplier, their price sheets and their purchase orders on one record. Import a supplier price sheet and the price board compares suppliers per milligram. Deliveries are received against the purchase order, every batch you receive arrives in quarantine with its own lot, and nothing goes on sale until its lab report passes your release rule. See it on the demo.
Common questions
- How do I know if a peptide supplier is legit?
- Check that each batch has its own report from a named independent lab that you can look up, that lot numbers match across the vial, report and invoice, and then test a sample you bought yourself. Paperwork alone is not enough; your own test is the deciding check.
- Should I test a supplier's product if they already send a COA?
- Yes. A supplier's report tells you what they say is in the batch. A blind test of a vial you bought tells you what you actually received. Do it before the first real order and again every few batches.
- How many suppliers should a new peptide company have?
- At least two for anything you sell in volume, so one running out or changing manufacturer does not leave you out of stock.