Onyx Peptides Review
EU-based (Slovakia) research peptide supplier using Janoshik Analytical for batch testing, with same-day EU dispatch and a cash-on-delivery checkout option. Distinct from several similarly-named "Onyx" suppliers in this market.
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Onyx Peptides sells its products exclusively for scientific research and development; any other use is prohibited. The authoritative product information and permitted use are those published by Onyx Peptides in its own shop, not on this page.
EU-domestic warehouse — fast delivery across Europe without customs or import duty risk.
The Verdict on Onyx Peptides
Onyx Peptides is a registered Slovak company (Vexio j. s. a.) that names its testing lab and publishes a clear methodology page, which clears a bar many vendors in this market do not. The one point of genuine reader caution is branding: at least three unrelated storefronts use "Onyx" in their name (onyxpeptides.com, onyxbiolabs.com, onyxresearch.shop, plus a near-identical officialonyxpeptides.com), and the negative reviews we found under "Onyx" trace to onyxresearch.shop specifically, not to this vendor. We could not locate an independent Trustpilot or review profile for onyxpeptides.com itself, so its actual customer-service track record remains unverified by us.
How Onyx Peptides Scores
Each criterion is scored independently out of 10. The star rating is the weighted average of these scores divided by two: lab transparency 30%, COA quality 20%, independent reputation 20%, shipping, catalog and value 10% each. Lab transparency is weighted most heavily, because a purity figure from an unnamed laboratory cannot be independently corroborated.
What We Found
Strengths
- Legal entity confirmed: Vexio j. s. a., registered in Banská Bystrica, Slovakia (IČO 54214530, founded 11 Nov 2021), verified in the Slovak commercial register (Obchodný register, Okresný súd Banská Bystrica, oddiel Sja, vložka 39/S).
- Names Janoshik Analytical, the same widely-used independent Czech laboratory several other vendors in this directory also use, and explains the batch-number-to-COA chain in plain language on its own site.
- EU-domestic dispatch (Slovakia) removes customs friction for European researchers, with same-day dispatch before 16:00 CET.
- Offers cash-on-delivery as a payment option, unusual in this market and useful for readers wary of prepaying an unfamiliar vendor.
Weaknesses & caveats
- Coded GLP products without published certificates. Semaglutide, tirzepatide and retatrutide are sold as GLP-I, GLP-II and GLP-III (the product descriptions identify each compound). No certificate is published for them; as with the rest of the catalog, reports are available on request only.
- No independent review profile located. We found no Trustpilot, Sitejabber, or comparable third-party review page for onyxpeptides.com specifically — reputation evidence beyond the vendor's own site is currently thin.
- Weak public financials for the operating entity. Vexio j. s. a.'s most recent filed accounts (FY2025) show 0 EUR revenue recorded, a net loss of -340 EUR, and negative equity of -2,640 EUR. This may simply reflect a young holding structure rather than the trading business, but readers extending credit or paying by bank transfer should be aware the corporate entity's filed financials are minimal.
- COAs are sent on request, not published. Compare to CertaPeptides, which hosts individual reports on the lab's own portal by default — Onyx requires the buyer to actively request the batch-matching certificate.
- We have not yet independently obtained and cross-checked a Janoshik report against an Onyx-supplied batch ourselves.
Lab Testing & COA Transparency
The single most useful question about any peptide vendor: can the purity claim be checked by someone other than the vendor?
| Testing lab publicly named | Yes — Janoshik Analytical (Prague, Czech Republic) |
|---|---|
| COA practice | Onyx states every batch is tested by Janoshik Analytical for HPLC purity, mass-spectrometry identity, LAL endotoxin level, and heavy metals, and that it is "a customer of the laboratory" with no ownership tie. Certificates are sent on request (by batch) rather than published site-wide, and the vendor's own quality page recommends verifying the report identifier directly with Janoshik. We have not yet requested and cross-checked an individual report ourselves, so treat this as vendor-stated practice pending our own verification. |
| Shipping | Ships from within the European Union (Slovakia), same-day before 16:00 CET, free over €100. No customs exposure for EU-based researchers. |
Claims We Could Not Verify
Onyx Peptides makes the following claims about itself. We found no independent corroboration for them. That does not make them false, but they rest on the vendor's word alone.
- Actual customer-service and fulfilment track record — no independent review platform for this specific storefront was located at time of review.
- The proportion of catalog batches with a currently valid, verifiable Janoshik report on file versus older or out-of-stock batches.
Onyx Peptides FAQ
QIs Onyx Peptides legit?
Onyx Peptides is a registered Slovak company (Vexio j. s. a.) that names its testing lab and publishes a clear methodology page, which clears a bar many vendors in this market do not. The one point of genuine reader caution is branding: at least three unrelated storefronts use "Onyx" in their name (onyxpeptides.com, onyxbiolabs.com, onyxresearch.shop, plus a near-identical officialonyxpeptides.com), and the negative reviews we found under "Onyx" trace to onyxresearch.shop specifically, not to this vendor. We could not locate an independent Trustpilot or review profile for onyxpeptides.com itself, so its actual customer-service track record remains unverified by us.
QIs there a Onyx Peptides promo code?
Yes. Code BIOHACK10 gives 10% OFF at checkout on Onyx Peptides. The discount does not change our rating: the score above is based on lab transparency, COA quality and third-party reputation only.
QDoes Onyx Peptides provide Certificates of Analysis?
Onyx states every batch is tested by Janoshik Analytical for HPLC purity, mass-spectrometry identity, LAL endotoxin level, and heavy metals, and that it is "a customer of the laboratory" with no ownership tie. Certificates are sent on request (by batch) rather than published site-wide, and the vendor's own quality page recommends verifying the report identifier directly with Janoshik. We have not yet requested and cross-checked an individual report ourselves, so treat this as vendor-stated practice pending our own verification. The testing laboratory is publicly identified as Janoshik Analytical (Prague, Czech Republic), which allows the documentation to be traced to a named third party.
QWhat are the main complaints about Onyx Peptides?
Coded GLP products without published certificates. Semaglutide, tirzepatide and retatrutide are sold as GLP-I, GLP-II and GLP-III (the product descriptions identify each compound). No certificate is published for them; as with the rest of the catalog, reports are available on request only. No independent review profile located. We found no Trustpilot, Sitejabber, or comparable third-party review page for onyxpeptides.com specifically — reputation evidence beyond the vendor's own site is currently thin. Weak public financials for the operating entity. Vexio j. s. a.'s most recent filed accounts (FY2025) show 0 EUR revenue recorded, a net loss of -340 EUR, and negative equity of -2,640 EUR. This may simply reflect a young holding structure rather than the trading business, but readers extending credit or paying by bank transfer should be aware the corporate entity's filed financials are minimal. COAs are sent on request, not published. Compare to CertaPeptides, which hosts individual reports on the lab's own portal by default — Onyx requires the buyer to actively request the batch-matching certificate. We have not yet independently obtained and cross-checked a Janoshik report against an Onyx-supplied batch ourselves.
QWhere does Onyx Peptides ship from and how fast?
Ships from within the European Union (Slovakia), same-day before 16:00 CET, free over €100. No customs exposure for EU-based researchers.
QDoes BiohackTested earn commission from Onyx Peptides?
BiohackTested earns affiliate commission on some vendor links. Commission does not affect ratings, rankings or editorial assessment, and no vendor sees a review before it is published. Weaknesses are documented for every vendor including those we earn from.
Sources
- Slovak commercial register entry (IČO 54214530)
- Vexio j. s. a. financial filings
- Onyx Peptides — Quality & Testing methodology page
- Janoshik Analytical
- Vendor site
Last reviewed: 2026-10-17. Vendor assessments are updated as new lab data and reputation signals appear.
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Independent review: This profile is an editorial directory listing based on public HPLC/COA documentation and community data. We may earn a commission on purchases through affiliate links, which does not affect our objective purity ratings.