After a while every peptide company starts to look the same. Clean website, a COA on every product page, a purity number in the high nineties, good reviews. There’s no obvious way to tell them apart from the outside.
I use three questions. Where was the finished product made, what are they actually testing for, and can I trace the vial in my hand back to that testing? All three came out of reading what laboratories find when they test this material, and the purity number on the certificate isn’t what settles any of them.
Why the purity number doesn’t settle it
An HPLC purity result answers one question. Of the material that absorbed UV light and came off that column under those specific conditions, what percentage of the total peak area sat under the main peak?
Every part of that sentence limits the answer. The detector runs at 214 to 220 nm or 280 nm, so anything that doesn’t absorb light there gets under-counted or missed completely, including salts, counterion and leftovers from synthesis. Anything that sticks to the column or washes straight through never enters the calculation. Closely related impurities can come off the column at the same moment as the main peak and hide inside it, which FDA describes as difficult to identify or quantify without sophisticated methods.
The biggest limitation is that the number is a percentage of itself. It tells you nothing about how much peptide is in the vial.
Breindahl and colleagues showed exactly that (Drug Test Anal 2015, PMID 24771717). They bought melanotan II from three online shops, all claiming 10 mg. Measured content came back between 4.32 and 8.84 mg, or 43% to 88% of what the label said. Not one vial met claim. A purity figure would have looked fine on all three.
The same extra amino acid keeps turning up
This is the finding that changed how I read a certificate.
Gajda and colleagues at the Danish doping laboratory analysed preparations seized by Danish customs and identified analogues of GHRP-2, GHRP-6, ipamorelin and modified GRF 1-29 (Drug Test Anal 2019, PMID 30136411). In every case the modification was identical. An extra glycine had been added to the front of the molecule. The authors concluded that detection methods need updating.
Krug and colleagues found the same defect independently, working across the German Sport University Cologne, the Norwegian doping laboratory, German federal customs and a Leibniz analytical institute (Growth Horm IGF Res 2018, PMID 29864719). Gly-GHRP-6, Gly-GHRP-2 and Gly-ipamorelin, with two of them confirmed by synthesising the suspected molecule from scratch and comparing it. The same paper reports a growth hormone product carrying 192 amino acids instead of 191, with an extra alanine, at a mass of 22,195 Da against 22,124 Da for the real thing.
Popławska and Błażewicz at the National Medicines Institute in Warsaw sequenced a novel seven-amino-acid peptide out of a seized injection vial, identified it as a glycine analogue of GHRP-2, and suggested it may be a deliberate route around doping detection (Drug Test Anal 2019, PMID 30051972).
An added glycine weighs 57.02 Da. On a chromatogram, the modified molecule still shows up as one sharp peak. A purity test would have called every one of these clean.
The wrong-molecule file doesn’t stop there. Esposito and colleagues found a GHRH analogue in a confiscated product where the chemistry at the tail end was incomplete, a difference of 0.98 Da, and called it evidence of poor pharmaceutical quality (Drug Test Anal 2014, PMID 25283153). Kohler and colleagues found a His6-tagged Long-R3-IGF-I in an injection vial and concluded it was more likely a leftover from biochemical research than something made for injection (Growth Horm IGF Res 2010, PMID 20675162). Walpurgis and colleagues characterised an 18 kDa protein turning up in several unlabelled products from independent sources and determined it was the product of an empty expression vector, meaning the manufacturing ran without the gene it was supposed to produce (Drug Test Anal 2014, PMID 25219942).
Identity and purity are two different measurements. That’s the whole reason my second question exists.
Question one: where was the finished product made?
The powder is not the product.
Where the raw peptide was synthesised and where the finished vial was formulated, filled and freeze-dried are two separate questions, and they frequently have two different answers. A certificate covering the raw material tells you about a sample that existed before most of the decisions affecting your vial had been made.
FDA states the principle directly in both of its peptide briefing documents. The stability, pharmacological activity and immunogenic properties of peptides are highly sensitive to the manufacturing process and to the quality attributes of the finished product.
The chemistry backs that up. Malgave and colleagues stressed semaglutide at 25, 40 and 60 °C for 28 days and at 80 °C for 7 days across a range of pH and buffer conditions, and identified 13 distinct degradation impurities, 6 of which appeared under every condition tested (Eur J Pharm Biopharm 2025, PMID 40490042). pH mattered more than anything else, and four impurities showed up only when water alone was the solvent. Those are formulation decisions, made after synthesis, by whoever fills the vial.
The ETH Zurich Laboratory of Pharmaceutical Analytics adds the part that matters most for this class (RSC Med Chem 2026, PMID 41541711). Peptides carrying an amide group at the tail end are markedly more vulnerable to these reactions, and the authors note the reactions occur under routine laboratory conditions. Ipamorelin, GHRP-6 and melanotan II all carry that group, and the one confirmed amidation failure found in a real seized product sits at exactly that site.
Preservatives are the same story. Roy and colleagues found aggregation in a freeze-dried protein reconstituted with benzyl alcohol (J Pharm Sci 2005, PMID 15614819), while Li and colleagues studied a 31-residue peptide by NMR and reported benzyl alcohol induced no aggregation at all, though 1% m-cresol produced insoluble aggregates amounting to a quarter of the peptide within 24 hours (Mol Pharm 2022, PMID 35917158). Preservative behaviour is peptide-specific and can’t be predicted from first principles, which is the entire reason formulation development exists as a job.
So when somebody tells me their supplier assures them the material is made in a clean facility, that answers a question about the powder. I want to know who formulated, filled and freeze-dried the vial.
The storage numbers everyone repeats came off product pages
Here’s how thin the published record actually is. FDA’s briefing documents contain the stability figures quoted all over this industry, meaning freeze-dried material stable at room temperature for 3 weeks and reconstituted solution stable 2 to 3 weeks at 4 °C and 3 to 4 months at -20 °C.
Check the footnotes. FDA’s sources for those numbers are commercial peptide vendor product web pages, cited because the agency couldn’t find characterization data anywhere in the published scientific literature.
The same windows appear word for word for two chemically unrelated compounds. Identical numbers for unrelated molecules is what boilerplate looks like. I went looking for peer-reviewed solution-stability data on GHRP-2, GHRP-6, ipamorelin or melanotan II and found nothing indexed.
Question two: what are they actually testing for?
Almost everybody posts a COA now. The useful question isn’t whether a company tests. It’s which measurements the certificate contains, and FDA has done the work of auditing real ones from this supply chain and publishing what it found.
On ipamorelin (briefing document, PCAC meeting 29 October 2024, fda.gov/media/182088), FDA recorded that the certificate submitted carried a purity limit of at least 95% with a result of 99.72%, and no impurity control at all to show what the impurity profile looked like. A wider search turned up one other certificate with a single impurity limit of under 2%, with no information on what those impurities were. For the acetate salt, FDA recorded no testing results for impurities, aggregates or endotoxin. For the free base, no certificate was supplied at all.
FDA concluded both forms were not well characterised, noted there’s no USP monograph for either after searching USP-NF, the European Pharmacopoeia and others, and said it couldn’t rule out immunogenicity from the uncharacterised impurities and aggregates, particularly for something meant to be injected.
The same document records a certificate that contradicted itself. Two nominating pharmacies submitted documents titled for the acetate salt that listed the CAS number, molecular formula and molecular weight of the free base. The title named one substance and the chemistry named another, in a package prepared for a federal advisory committee under the most scrutiny a document in this supply chain will ever receive.
The BPC-157 briefing (PCAC meeting 23 to 24 July 2026, fda.gov/media/193343) reads the same way. One certificate reported 97.8% purity with maximum individual and total impurity results of 1.1% and 2.2%, and FDA’s comment was that the impurity profiles are unclear because the impurities were never identified. The second showed 98.34% purity and no impurity control whatsoever. Neither carried residual solvent testing, and neither showed whether bioburden or endotoxin testing existed.
The measurements FDA says an injectable needs
FDA lists these in both documents, and every certificate it read was missing most of them.
- Identity, confirmed against a reference standard
- Impurities identified by name, not just totalled as a percentage
- Sterility
- Bacterial endotoxins
- Bioburden
- Aggregates
- Foreign particulates
- Residual solvents
Add water content and counterion content to that list. Those two determine how much actual peptide a stated milligram figure represents, which is the gap Breindahl measured.
Count what’s on the certificate rather than counting how many tests a company advertises. A long list of tests that skips identity and endotoxin tells you less than a short list that includes them.
Why identity is the one that can’t be taken on trust
US drug GMP settles this in a single paragraph. 21 CFR 211.84(d)(1) requires at least one test to verify the identity of every component of a drug product. Subsection (d)(2) permits a manufacturer to accept a supplier’s report of analysis only if it runs its own identity test on that component and periodically validates the supplier’s results.
A licensed drug manufacturer is not allowed to take a supplier’s certificate as proof of identity. It has to test every lot itself. Anyone holding nothing but a PDF is standing in a position the regulations specifically forbid a regulated company from standing in.
FDA also explains why identity is the hard measurement. Peptide synthesis throws off impurities from incomplete coupling, truncations and side reactions, and those impurities are structurally similar to the target peptide. Structurally similar peptides are exactly the species most likely to hide under the main peak.
What testing of seized material has found
| Study | Material | Finding |
|---|---|---|
| Weber et al., Subst Use Misuse 2017, PMID 28156209 | 1,190 products seized at the Swiss border, 146 labelled as peptide hormones or growth factors | Fewer than 20% contained the claimed substance in the claimed amount |
| Høj et al., Drug Test Anal 2021, PMID 33686802 | 36 samples submitted to Danish forensic chemistry, 2019 caseload | 9 of 36 (25%) contained no peptides or proteins at all |
| Krug et al., Eur J Clin Pharmacol 2014, PMID 25168622 | 337 black-market products, German customs and the Cologne laboratory, 2010 to 2013 | 67 active ingredients found, 49 of them WADA-prohibited. Peptide hormones and growth factors were 12.8% of findings |
| Hullstein et al., Drug Test Anal 2015, PMID 26607218 | Confiscated products, Norwegian doping laboratory, 2011 to 2014 | 28% contained peptide or protein-based doping substances |
| Fabresse et al., Forensic Sci Int 2021, PMID 33838562 | 110 products seized from French bodybuilders, 2016 to 2019 | Of 75 seized pharmaceuticals, 33% substandard on dose, 32% counterfeit on formulation, 19% genuine |
| Barrios et al., Drug Test Anal 2025, PMID 40551438 | 324 samples, 14 laboratories, 13 countries, 5 years | 24% were sold to the buyer as dietary supplements. Some products were overdosed rather than under |
A 2024 Cologne report covering 41 products found that 53% of ingredients were undeclared or falsely declared, and describes a product labelled as semaglutide that contained insulin. Read that denominator before repeating it. The 53% is of 72 findings across 21 drugs rather than of the 41 products, and peptide hormones were only about 7% of the compounds identified. Anabolic agents were 89%. It’s a conference proceedings chapter rather than a peer-reviewed paper (Recent Advances in Doping Analysis vol 33, DOI 10.25847/mdi.2025.033).
One figure you’ll see quoted in peptide arguments belongs to a different product class entirely. A meta-analysis of 19 studies and 5,413 anabolic steroid samples found 36% counterfeit and a further 37% substandard (Magnolini et al., BMC Public Health 2022, PMID 35842594). That’s steroids. It shouldn’t be used as a peptide failure rate.
The one study that bought from sellers and tested what showed up
Ashraf and colleagues ran the only test-purchase study in this space with full analytical follow-through (J Med Internet Res 2024, PMID 39509151). The group screened 1,080 search-result links, identified 59 illegal online pharmacy sites, and measured more than 4.7 million visits to the top 30 affiliated domains across three months. They placed six orders and three vials arrived. All three prefilled-pen orders were straight non-delivery scams, so half the money bought nothing at all.
The three vials that did arrive came back sterile. Content ran over label in every case, by 28.56%, 33.58% and 38.69%. The chromatograms showed a single peak per sample with no peptide-like impurities found. Packaging and labelling failed on 13 to 14 of 22 criteria.
That paper is also the source of a number I see misused constantly. Its reported values of 7.7%, 8.97% and 14.37%, set against a vendor claim of at least 99%, are not purity in the sense the vendor meant. The full text defines them as peptide mass divided by total powder mass in the vial. In any freeze-dried injectable that fraction is legitimately low, because most of the cake is excipient, buffer salt, counterion and residual water. The vendor’s 99% is a peak-area figure. Putting the two side by side compares two different measurements.
Two caveats on the same paper, because I’d rather you have them. The endotoxin results were reported as under 2.1645, under 2.8658, and 8.9511 EU/mg, so two of the three sit below the level where the method gives a real number, and the authors applied no pharmacopoeial limit and made no pass or fail call. On disclosure, two authors work for a data-science startup funded by public-health contracts, one as co-founder and part owner, and that same author edits a journal in the publishing family that ran the paper.
Question three: can you trace the vial back to the batch?
This one is simple to check and it’s where most of the industry falls down.
Look at the vial in your hand. Is there a batch number on it? Now look at the certificate. Does that certificate cover that batch, and is it dated in an order that makes sense? A certificate with no matching lot number, or one dated well before your shipment, connects to nothing you’re holding.
Posting a good certificate on a website and being able to tie the vial you received back to it are two different capabilities. Only one of them is evidence about your product.
Two things worth knowing while you check. ISO 17025 accreditation is scope-specific, which means it confirms a laboratory is competent at particular methods within its accredited scope. It says nothing about the product, the sampling, or whether the sample represented the batch. And a laboratory reports what it was asked to test, so “third-party tested” against a purity-only scope is a completely true statement that answers none of the questions above.
Batch consistency is unmeasured, not measured and bad
I went looking for a study that tested multiple lots of the same labelled product from the same source and couldn’t find one. Anyone telling you a source is batch-consistent is going past the data, and so is anyone telling you it’s batch chaos. What has been measured is the spread between sources, and that spread is wide.
There’s also a structural reason not to assume constancy. The Warsaw group framed its novel glycine analogue as a possible route around detection. If somebody in the chain has a reason to change the molecule, you can’t assume the molecule stays the same from one order to the next, which makes the ability to check each batch the only real handle you have.
Research use only is not a shield
Since 23 March 2020, under the final rule defining biological product (85 FR 10057), any chain of 40 or fewer amino acids is a peptide and is regulated as a drug. BPC-157 at 15 residues, ipamorelin at 5 and melanotan II at 7 all sit on the drug side of that line.
Peptides currently in FDA’s category 2, meaning documented but carrying identified safety risks, include GHRP-2, GHRP-6, ipamorelin acetate, ibutamoren mesylate and kisspeptin-10. A claim circulating widely says FDA removed a dozen peptides from category 2. FDA’s page, last updated 22 April 2026, lists those substances under a separate heading stating they were withdrawn by the nominators. The nominators withdrew them and FDA cleared nothing. Those substances still have no monograph, still aren’t components of approved drugs, and still aren’t on the Bulks List.
The committee voting record shows how these members weigh documentation. At the 29 October 2024 meeting (minutes at fda.gov/media/185412), ipamorelin free base was rejected 0 yes to 12 no with 1 abstention, and the acetate lost by the same margin. Kisspeptin-10 went down 0 to 11 and ibutamoren mesylate 1 to 13. The recorded reasoning on ipamorelin was a lack of information supporting safety and efficacy, and on another substance members cited the absence of a USP monograph or a certificate of analysis as grounds to vote no.
As for the disclaimer printed on the vial, FDA’s position is settled and recent. Warning letter 735063, dated 24 August 2026, states that despite labelling products for research use only and not for human or veterinary use, evidence from the seller’s website established the products were intended as drugs for human use. Under 21 CFR 201.128, intended use is established by objective evidence of the seller’s intent. Roughly fourteen of these letters have issued since February 2025, five of them on a single day.
One more correction while we’re here. The impurity thresholds people quote, where anything above 0.5% is unacceptable and the 0.10 to 0.5% band needs identification and justification, aren’t general peptide rules. They came from a May 2021 guidance covering five named peptides in a narrow generic-drug scenario, and FDA has since withdrawn that guidance on the grounds that it no longer reflects current scientific thinking. There’s no approved specification for ipamorelin, BPC-157, TB-500 or melanotan II. Nothing exists to be in spec against.
What this comes down to
The failure mode in this market isn’t the one most people picture. The best test-purchase data we have found sterile vials, clean single-peak chromatograms and content running over label rather than under. The documented problem is that no specification exists to test against, no lot is traceable, no identity method is routinely applied, and the one document you’re handed answers a question nobody needed answered.
That’s why I’m not looking at the purity number. I’m asking where the finished vial was made, which measurements the certificate actually contains, and whether the batch number on my vial appears on the testing.
This article is a review of published research and regulatory documents. Nothing here is a recommendation to use any compound. The substances discussed are research-use-only materials, they are not approved for human use, and nothing above describes how to use them.
This is not medical advice. Research use only.
