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What we read

Janoshik's public-tests database, the published HPLC and mass-spec result sets from approximately 110 vendor batches between January 2024 and April 2026, the ERP SS31 endotoxin case study, Kilo Biotechnology's analysis of retatrutide identity fraud, and approximately 60 r/Peptides post-mortems on individual failed orders.

Most reviewers rank vendors. We catalog how they fail. The taxonomy below is descriptive — every category is documented in public test data with at least one specific batch we cite.

The eight failure modes

01 — Identity swap

The molecule in the vial is not the molecule on the label. The most-cited 2025 example: roughly 23% of retatrutide samples submitted to Janoshik contained exendin-4 analogs instead of authentic retatrutide. Identity swap is the most expensive failure mode for the buyer because it is undetectable without mass spectrometry — HPLC alone can show acceptable purity for the wrong molecule.

Detection difficulty: Hard. Requires mass-spec, not just HPLC. Prevalence: High in novel compounds (retatrutide, novel GLP analogs); low in well-established compounds (BPC-157, GHK-Cu). Vendor signal: A vendor whose COA only shows HPLC purity without mass-spec identity is leaving identity fraud as an unconfirmed gap.

02 — Under-fill

The vial contains less material than the label claims. The ERP SS31 case documented vials labeled 50 mg that on independent quantification contained only 44.10 mg — an 11.8% under-fill. The buyer paid the full per-mg price for a fractional dose.

Detection difficulty: Medium. Requires quantitative testing; visible on Janoshik's full assay package. Prevalence: Highest in low-margin SKUs and in late-batch production. Vendor signal: COAs that report only purity (a percentage) without quantity (the actual mg figure) are concealing this dimension.

03 — Under-purity

The molecule is correct, the quantity is correct, but the chemistry is not as pure as claimed. The pattern is a vendor claiming 99%+ purity on the COA while the independent test shows 71–91% — typical of the lower-tier vendor band per Janoshik's 2024 reporting.

Detection difficulty: Easy. HPLC catches it directly. Prevalence: Pervasive in lower-tier vendors. The 43% Janoshik failure rate is dominated by this category. Vendor signal: Vendors who only post in-house COAs, never independent.

04 — Endotoxin contamination

The peptide is correct in identity, quantity, and purity, but the vial contains bacterial endotoxin above safe research thresholds. The ERP SS31 case again: endotoxin levels measured above the validated reporting range, with an estimated value of 26.79 EU/vial — well above the 0.5 EU/mL acceptable for parenteral research material.

Detection difficulty: Hard. Requires LAL testing, not on standard HPLC reports. Prevalence: Underreported because most COAs do not include endotoxin testing. Likely understated in public data. Vendor signal: Vendors who include endotoxin testing in their full COA package are signalling production discipline; vendors who do not include it are signalling cost-optimization.

05 — Counterfeit COA

The COA itself is fabricated. The lab named on the certificate either does not exist, or does exist but never tested the vial in question. Janoshik's QR-verified COAs were specifically designed to defeat this attack — the QR resolves to a record on Janoshik's servers that the vendor cannot edit.

Detection difficulty: Easy if the COA is from Janoshik (verify the QR). Hard if the COA names a less-known lab. Prevalence: Low at the top of the market; concentrated in fly-by-night vendors. Vendor signal: Any COA from a lab whose name does not appear in the Janoshik / Finnrick / Peptide Protocol Wiki cross-references.

06 — Sterility failure

Vials are not sterile. Less common than endotoxin issues but more severe when present.

Detection difficulty: Hard. Requires sterility testing on the specific vial. Prevalence: Rare. Vendor signal: GMP-claimed vendors should publish sterility test results; vendors who claim "lab-quality" without producing sterility documentation are not actually GMP.

07 — Generic-batch COA

One COA is reused across batches that share nothing but the SKU label. A persistent failure mode in the lower-tier vendor band, and the most common pattern Janoshik flags as "non-batch-specific testing."

Detection difficulty: Easy. Check whether the COA's batch ID matches the vial's batch ID. Prevalence: Pervasive in vendors that publish COAs but not batch-specific COAs. Vendor signal: A COA without a batch number, lot ID, or date matching your specific vial.

08 — Shipping or delivery failure

Order is paid but never arrives, or arrives in unusable condition (cold chain broken, vials cracked, customs seizure with no replacement). Less a quality failure than an operational one, but financially equivalent for the buyer.

Detection difficulty: Visible only after ordering. Prevalence: Concentrated in vendors with weak customer-service infrastructure or vendors shipping into jurisdictions with stricter customs (Germany, UK, Australia). Vendor signal: Vendor explicitly states their replacement / refund policy for customs seizure, or doesn't.

Which modes are most common

In Janoshik's public dataset weighted by 2024–2025 sample count, the rank order of failure prevalence is:

1. Under-purity (the 43% headline)
2. Generic-batch COAs (a structural rather than chemistry failure)
3. Identity swap (concentrated in retatrutide and novel GLPs)
4. Under-fill (concentrated in higher-mg SKUs)
5. Endotoxin (likely underreported because rarely tested)
6. Counterfeit COA (low at top tier; spike in fly-by-night vendors)
7. Sterility failure (rare)
8. Shipping failure (operational; not a chemistry signal)

Which modes are hardest to catch before ordering

Ranked by detection difficulty:

1. Endotoxin contamination — needs LAL testing the vendor must commission
2. Identity swap — needs mass-spec the vendor or buyer must commission
3. Under-fill — needs quantitative testing
4. Sterility failure — needs sterility testing
5. Counterfeit COA — easy if vendor uses Janoshik QR; otherwise hard
6. Under-purity — easy with any HPLC test
7. Generic-batch COA — easy by inspection
8. Shipping failure — easy after the fact, impossible before

This ranking is the buyer's pre-purchase risk surface. The first four require commissioned testing; the last four can be triaged from the vendor's published COA practices.

Reader checklist

For a vendor you are about to place a recurring order with, verify in this order:

1. Mass-spec identity is published on the COA package, not just HPLC purity (defends against #1)
2. Quantitative content is reported, not just purity percentage (defends against #2)
3. Janoshik QR or named-lab COA is provided with batch ID matching your vial (defends against #5, #7)
4. Endotoxin and sterility are tested for at least sample batches (defends against #4, #6)
5. HPLC purity is within 2 percentage points of label claim (defends against #3)
6. Customs and replacement policy is published in writing (defends against #8)

A vendor that satisfies six of these criteria is in the top tier. A vendor that satisfies four or fewer is a vendor we would not recommend, regardless of headline price or community reputation.

What we did not read

This taxonomy does not include the population of buyers who never test their vials and never report on community forums — the silent majority whose experience is invisible to the public-data analysis. The next iteration of this piece will incorporate the Janoshik commissioned-test population (where a buyer pays for testing on a vial they bought), which is a different sampling than the vendor-submitted population.

Sources

• Janoshik public tests database
• Is retatrutide legit? Lab-tested purity reports — Kilo Biotechnology
• ERP SS31 endotoxin case — GLP-1 Forum
• Janoshik Analytical review — Peptide Protocol Wiki
• Finnrick testing methodology