The four gates
Every supplier passes through four gates in order. Clearing one is how you reach the next.
- Auto-disqualifiers. Hard stops. Any single one ends the evaluation.
- Seven quality criteria. Scored individually. Most of the work happens here.
- Commercial terms. Assessed only after quality is scored, so they cannot influence it.
- Strategic fit. Whether listing a supplier strengthens this page or just lengthens it.
Gate 1: auto-disqualifiers
- FDA enforcement action.Any warning letter, consent order or criminal case, checked against the FDA’s own compliance records.
- No certificate, or in-house-only testing.A certificate from the vendor’s own laboratory does not clear this.
- Lot number mismatch. The batch on the certificate must match the batch printed on the vial.
- Prices far below the market. A price well under what the same compound and form costs everywhere else is a signal, not a bargain.
- Hype with no data. Urgency selling and unsupported claims.
Gate 2: the seven criteria
1. Independent, per-batch certificate. From a named third-party laboratory, specific to the batch you receive rather than a template reused across batches. A third-party laboratory is accountable for its results in a way an in-house one is not.
2. HPLC purity, with the chromatogram. High-performance liquid chromatography measures how much of the vial is the compound and how much is something else. We want the percentage and the visual trace, not just a number typed on a page.
3. Mass-spectrometry identity. Confirms the compound is chemically what the label says. Purity testing alone cannot catch a substitution, because a different compound can still be pure.
4. Endotoxin and sterility testing. Endotoxins are bacterial fragments that trigger an immune response. For anything injectable this is not optional.
5. Lot number matches the vial. Your proof that the certificate you are reading applies to the vial in your hand, rather than to a different batch.
6. Transparent business. A real contact route, a published returns policy, sensible payment methods, and a company you could actually reach if something went wrong.
7. Independent corroboration. Testing or grading by someone with no stake in the sale. See the limits section below, because this is the criterion we are weakest on.
Where our verification stops
We check the paperwork, not the vial.
That means confirming the certificate is real and publicly reachable, that it names an outside laboratory rather than the vendor’s own, that it covers the specific batch you receive, and that the lot number matches. Where a certificate sits on the testing laboratory’s own site instead of being re-uploaded by the vendor, we note it, because it is harder to alter.
What we have not done is put that vial through our own assay. Commissioned testing is next on the list as part of our ongoing development roadmap.
Testing laboratories
We record which laboratory or laboratories a vendor uses, and we hold that vendor to naming them. Where a supplier uses more than one, we list all of them, not whichever is most convenient. What we do not do is rate the laboratories themselves.
Our assessment is of the supplier: whether they publish real, batch-specific, third-party documentation and stand behind it. Ranking the laboratories is a different exercise, and not one we take on. We give you the name and the certificate, and you can take that as far as you want to.
Affiliate relationships
We earn a commission when someone buys through a link on our sources page. Two things follow from that, and we hold to both.
Commercial terms are discussed only after quality scoring is finished, so they cannot affect whether or how a supplier is listed. And we publish where a supplier falls short, not only where it passes. A page that only ever said good things would not be worth reading.
Re-checking
Suppliers change. A vendor clean today can take an enforcement action tomorrow, move domain, or quietly stop publishing certificates. We re-check the perishable parts of this list and record when each entry was last reviewed.
How to use this
Read the individual entries, not just this page. Each shows which criteria a supplier meets and which it does not, and the date we last checked. Verification is a snapshot: confirm the current certificate yourself before buying.