How to tell if your peptides are real: what to test first and what to check on a COA

Only a lab test can tell you if your peptides are real

“Real” has three parts that a buyer can check: the vial holds the peptide on the label, it holds about the amount on the label, and that peptide is reasonably pure. A lab measures each one. Identity comes from LC-MS, the amount from a content assay against a reference standard, and purity from HPLC. Nothing you can see, smell or weigh at home answers these questions, and no home kit does either. The guide to peptide test kits explains why.

Contamination is a separate question. A vial can hold the right peptide in the right amount and still carry endotoxin or microbes. Those need their own tests. A lab result shows what was in the vial; it cannot say whether a product is safe to use.

Question	Test	What a good result shows
Is it the right peptide?	Identity (LC-MS)	Expected and observed mass, close together, with an error value
Is the amount right?	Content per vial	mg as free base, with uncertainty and % of the label claim
Is it pure?	Purity (HPLC)	% peak area at a stated wavelength, with the chromatogram
Is it contaminated?	Endotoxin (LAL), Sterility (USP <71>, 14 days)	EU per mg and per vial; no growth after 14 days of incubation

What to test first: identity, then content

Identity by mass

Start with identity. A wrong peptide, or an empty vial, makes every other number meaningless. The identity test should match the mass of the main peptide to the calculated mass of the peptide on the label.

Retention time is not enough on its own. ICH Q6A, the international guideline on specifications, says retention time alone “is not regarded as being specific”. Similar peptides can leave the column at nearly the same time. GLP-1 peptides show why this matters: retatrutide and tirzepatide differ by about 82 Da on molecules of about 4,700 to 4,800 Da. Buyers have reported vials sold as one GLP-1 peptide that held another, and a mass match is the check that tells them apart.

If you doubt a GLP-1 label, a blind GLP-1 identification asks the lab to name the peptide without being told what the label says.

Content per vial

Next, the amount. A content test reports mg of the peptide, as free base, against a reference standard, and the result as a % of the label. It catches the two other common problems: underfilled vials and overfilled ones. Finnrick’s default standard fails a vial that is more than 35% above or below its label.

Ask for the basis. Powder also holds water and counter-ions such as TFA or acetate, so a result on total powder reads higher than a result as free base.

Then purity and safety tests

HPLC purity tells you what share of the UV-absorbing material is the main peptide. It is useful, but a 99% purity result can sit on a vial with half its label amount, so purity never replaces content. Endotoxin and sterility come next if they matter for your research. Each needs its own unopened vials.

How often published samples fail

Failures are common in public data. Finnrick, a US platform that publishes results from community-submitted samples, had 791 published BPC-157 tests in its data to 20 September 2026. 395 failed its default standard, about half of classifiable samples. Retatrutide failed about 21% of the time (824 of 3,858 tests), and GHK-Cu about 13%.

A fail is not always a fake. Finnrick’s default standard also fails a sample of the right peptide at 99.4% purity, or a vial 40% over its label. The guide to peptide fail rates ranks products, and the guide to fake peptides sorts the failure types.

For GLP-1 medicines sold illegally, the FDA lists the same risks a lab test looks for: the wrong ingredients, too little, too much or no active ingredient at all.

What you cannot tell by looking

Some checks feel useful but answer nothing about the contents:

• The powder. Freeze-dried peptides look much the same, whichever peptide is in the vial.
• The label and cap. They show who packed the vial and which lot it belongs to. They can be copied.
• The price. A high price does not prove identity, and a low one does not prove a fake.
• A PDF on a product page. It can be real, reused from another batch, or edited.

Looks do have one use: a broken seal, a cracked vial or a lot number that differs from the COA is a reason to ask questions before you rely on anything.

How to check a seller’s COA

A COA is only as good as what it shows and whether you can check it. Read it in this order:

1. Lot number. It should match the lot on your vial exactly.
2. Where it opens. Open the report on the lab’s own website, from the lab’s lookup page or QR code, and compare it with the copy you were sent.
3. Identity evidence. Look for an expected mass, an observed mass and an error value. In our September 2026 review of 26 certificate formats from peptide labs, 12 showed a mass spectrum, and only 3 printed the expected and observed mass side by side with an error value.
4. Raw data. A chromatogram and a peak table behind the purity number. A bare “99.8%” cannot be checked.
5. mg with a basis. Content per vial, stated as free base or as total powder.
6. Dates and scope. The test date, and the tests actually run. If the lab shows an accreditation mark, check that its published scope covers that test.
7. Who ordered it. None of the 26 certificate formats in our review stated the client’s relationship to the lab.

The guides on how to verify a peptide COA and signs of a fake peptide COA go through each check. Our page on how to read a COA explains each section of a report.

Test your own vial

Even a genuine COA covers the sample the seller sent, not the vial in your hand. One report covers one sample. The only way to know about your vial is to test it, or a vial from the same lot that you picked yourself.

Three ways to make the result count:

• Withhold the label claim. A lab that does not know the claimed mg cannot lean on it.
• Test more than one vial. One vial tells you about that vial. Three or more from different kits show how much a batch varies.
• Share the cost. A group test splits one lab order across several buyers of the same batch.

The guide on how to get peptides tested walks through quotes, packing and shipping.

What HK Analytical does

We test the questions above in one order: identity (LC-MS), purity (HPLC) and content per vial, plus blind GLP-1 identification, endotoxin (LAL), Sterility (USP <71>, 14 days), residual solvents, counter-ion, water content and vial-to-vial consistency, in any mix. Results within days of receipt. Sterility (USP <71>, 14 days) is the one test that takes 14 days, because the method incubates for 14 days. Each report carries the raw data behind every number, our photo of the vial as received, and a statement of how the client is related to HK Analytical, inside a signed record you can check at hkanalytical.com/verify. We do not hold ISO/IEC 17025 accreditation. See the example report or request a quote.