Which lab do vendors accept? Why sellers honour some labs' results and not others

Which lab do vendors accept: the short answer

There is no shared list. Each seller writes its own refund or guarantee terms and decides which lab results it will honour. In practice, buyers on Reddit report that some sellers accept refund claims only with results from Janoshik, and some also accept Freedom Diagnostics (r/Biohacking). Buyers warn that a test at a lab the seller does not honour can mean paying for a second test (r/Peptidesource; r/PeptideDiscussion).

So the first step is simple. Before you order a test, read the seller’s terms or ask in writing: which labs do you accept, and what do you need from the report?

Why some labs’ results carry weight with sellers

Sellers are not judging the lab’s science alone. They are judging whether they can trust that a report is real, belongs to their product and lot, and measures the same thing their own testing measures. Five things decide that.

A long public record

Janoshik describes more than ten years of experience in chemical analysis (Janoshik) and ranks first in Peptides Weekly’s Q3 2026 lab guide; Freedom Diagnostics ranks second (Peptides Weekly). Freedom has the largest certificate count in Peptigrity’s lab directory (4,790), and Janoshik has 2,556 (Peptigrity). Sellers have seen thousands of these reports, often on their own products, and know how the numbers usually run.

A lookup that proves the report is genuine

A seller’s main fear is a forged or borrowed report. Janoshik reports carry a task number and a unique key that anyone can check on its verification page (Janoshik). Freedom Diagnostics offers a public lookup by company name or code (Freedom Diagnostics). A result the seller can confirm on the lab’s own site is easy to honour. A screenshot is not.

Rating sites reward the same thing. Peptigrity marks each certificate as lab-verified, unverified, “lab has no portal” or “report no. not found” (Peptigrity). Disclosed Labs scores a report mirrored from the lab at 100 and a named lab with no check at 75 (Disclosed Labs). How to run these checks yourself: how to verify a peptide COA.

Identity by mass, with data

A seller who is told its vial holds the wrong peptide will ask how the lab knows. A mass match by LC-MS, with the expected and measured mass and the spectrum, answers that. A peptide name printed with no evidence invites a dispute.

Numbers the seller can compare

Labs disagree on the same batch, and sellers know it. In a published comparison of one retatrutide batch across five labs and the seller’s report, mass results ran from 10.18 to 12.80 mg, a 26% spread (Peptide Critic). In another single published case, Janoshik and Chromate measured about 30 mg per vial on one batch and Krause measured 26 mg (graymarket).

The labs gave reasons. Janoshik says it standardises its own reference standards and reports net peptide, without counter-ions. BTLabs pointed to method differences and the lack of USP standards (Krysia). Different bases give different mg. A seller that releases batches on one lab’s numbers may doubt a lab whose basis it has never compared. Our guide to why labs disagree explains the main causes.

Weight on rating sites

Merit Verified weights each certificate by its lab’s quality score and gives accreditation the most weight in that score (Merit Verified). An accreditation logo alone settles little: Krysia’s Substack showed that some labs’ ISO/IEC 17025 certificates do not cover their peptide tests (Krysia). Check the scope, not the logo.

What a seller checks before honouring a result

What the seller checks	Why	What you can do
The report is genuine	Forged and borrowed reports exist	Use a lab with a per-report lookup
The lot matches	A report covers one lot	Photograph the lot and cap before shipping
The vial was sealed	An opened vial can be swapped or contaminated	Send crimped, unopened vials
The lab’s own photo of the vial	Proves which vial was tested	Choose a lab that photographs vials on receipt
Identity evidence	A name without data invites dispute	Ask for LC-MS with expected and measured mass
The mg basis	Net peptide and gross powder differ	Choose a report that states its basis
A sample left for a re-test	A seller may ask for one	Keep one sealed vial back

How to make your own test count

1. Read the terms first. Note which labs the seller names and what the report must show.
2. Buy for evidence. If you can, keep a second sealed vial of the same lot.
3. Document before you ship. Photograph each vial with its lot and cap. Keep the order record.
4. Withhold the label claim. A result found without the label in view is harder to argue with.
5. Pick a lab whose reports anyone can verify, with raw data and mass identity.
6. For a large claim, test twice. Send one vial to a lab the seller accepts and one to a second lab. A group test spreads the cost; see how to run a peptide group test.

When a seller rejects your result

Ask for the reason in writing. Send the verification link and the raw data, not only the PDF. Offer a re-test of a sealed vial from the same lot at a lab the seller names. Lab practice supports this: WHO guidance asks quality control labs to keep retained samples large enough for at least two re-analyses (WHO TRS 957), so ask your lab how long it keeps yours.

Keep in mind what a result proves. It shows what was in the vial the lab received. It cannot prove that every vial of the batch is the same. Several random vials from different kits make a far stronger case.

What HK Analytical does for this question

Every number in our report comes with its raw data, including the chromatogram and mass spectrum. The report is a signed record with a private link that anyone holding the report ID and access key can check on /verify. It carries our own photo of the vial as received (chain of custody) and states how the client relates to HK Analytical. Reports are never edited; a correction makes a new version and marks the old one superseded (quality). We do not hold ISO/IEC 17025 accreditation. See the example report.