Verification · Buyer FAQ
The peptide buyer's FAQ: choosing a peptide, checking the COA, reading the numbers
Twelve questions, three themes: choosing the peptide and the seller, checking the COA before you pay, and reading the identity, purity, and content numbers once the document is in front of you. Straight answers, no marketing.
Choosing the peptide and the seller
The first decision is the molecule; the second is who you buy it from. Both are easier than they look once you separate them. Choose the molecule from published research — sequence, mechanism, stability — and treat anything beyond that as a question for a qualified professional. CertikLabs covers chemistry and verification only, never dosing or clinical guidance.
Choosing the seller is a verification problem. The short version: a serious seller publishes a batch-specific COA for the current lot, names the lab, and makes the document checkable without going through them. The full checklist is in how to buy peptides with a COA you can trust and how to spot a trustworthy peptide supplier.
Checking the COA before you pay
Three checks, five minutes: the lot number matches what ships today; the lab is named and exists independently of the seller; and the document has a verification route — a URL, QR code, or report number that resolves at the lab. Fail any one and the document is decoration.
For the foundations — what a COA is, the four numbers it must show, and who should issue it — start with what is a peptide COA?. For the forgery patterns, see the fake COA checklist.
Reading the test numbers
Four numbers carry the weight. Identity (LC-MS): observed mass vs the theoretical mass from the sequence. Purity (HPLC): a percentage with the method stated — without conditions it can't be reproduced. Content: milligrams of actual peptide per vial, which purity never tells you. Endotoxin: a numeric EU value with the method (LAL or rFC) named, required for anything entering a living system.
The line-by-line walkthrough of every section — header, chromatogram, counter-ion, residual solvents, signature — is in how to read a peptide COA, and the quick-fire version lives in the peptide COA FAQ.
When the paperwork isn't enough
Seller documentation is still the seller's evidence. The strongest check is one you control: send a vial to an independent lab for identity, purity, and content measured from the physical product. That's the model CertikLabs is built on — the lab has no stake in the sale, and the result publishes against a specific batch with a record any buyer can open.
Weighing the cost? The item-by-item guides cover BPC-157, TB-500, semaglutide, and retatrutide. Curious how a verified result reaches you? See how CertikLabs credibility works.
Frequently asked questions
How do I choose which peptide to buy?
Start from the published research on the molecule itself — its sequence, its studied mechanism, and its known stability — not from marketing claims. CertikLabs covers chemistry and analytical verification only; we never give dosing or clinical guidance. Once you've chosen a molecule, the buying decision becomes a verification decision: which seller can prove what's in the vial.
How do I choose a peptide seller?
Look for a seller who publishes a batch-specific COA for the current lot, names the lab that issued it, and offers a way to verify the document independently of their own website. Sellers who expect to be checked — and make checking easy — are the ones worth ordering from.
What is the single most important thing on a peptide COA?
The lot number. A COA is a result for one production run. If the lot on the document doesn't match the lot on your vial, every other number on the page is irrelevant to what you're holding.
What does '99% purity' actually mean on a COA?
It means 99% of the UV-absorbing material in the HPLC run was the main peak. It says nothing about how much actual peptide is in the vial (content), whether the main peak is the right molecule (identity), or whether the vial is free of endotoxin. Purity is one number of four that matter.
What is the difference between purity and content?
Purity is a percentage: how much of the detected material is the target peptide. Content is a mass: how many milligrams of actual peptide are in the vial. Lyophilized peptides carry water and counter-ion, so a '5 mg' vial often contains 3.8–4.5 mg of active peptide. A COA that reports purity but not content leaves the most practical question unanswered.
How do I check the identity result?
Look for mass spectrometry: an observed mass next to the theoretical mass calculated from the peptide's sequence, with a small deviation. You can sanity-check the theoretical mass yourself from the published sequence. 'Identity: confirmed' with no numbers is a claim, not a measurement.
Does an HPLC purity number need a method stated?
Yes. Purity depends on the column, mobile phase, gradient, and detection wavelength. A purity number without method conditions cannot be reproduced or challenged — treat it as unverified.
When does a COA need an endotoxin result?
For anything entering a living system. Endotoxin is reported as a numeric value in EU (endotoxin units) with the method named — LAL or recombinant Factor C (rFC). Research-grade material doesn't require it; injectable-grade material does.
Is a vendor-issued COA trustworthy?
It's evidence with a conflict of interest attached. The methods may be sound, but the entity reporting the result profits from it. An independent third-party lab has no stake in the sale — same instruments, different incentives. Prefer third-party, and verify either kind directly with the issuing lab.
How do I verify a COA is real and not recycled?
Three checks: the lot number matches your vial; the issuing lab exists independently and will confirm the report; and any verification URL, QR code, or report number resolves at the lab, not just on the seller's site. The same COA appearing across multiple products, or perfect identical numbers on every batch, are classic signs of a recycled document.
What if the seller can't produce a COA for the current lot?
Treat the product as untested. You can still buy and verify independently — send a vial to a lab yourself for identity, purity, and content — but order with the knowledge that no evidence about the batch exists.
Can I trust a QR code or seal on the packaging?
Only if it resolves to a live record at the testing lab, and the lot on that record matches your vial. A badge or QR alone never proves a result — the record behind it does.