Clinical perspective, offered as context rather than as advice. The distinction that resolves most of these threads is between what is true on average and what is true for one person. Both are real; they answer different questions and get quoted as if they were the same one.
Worth separating that from vendor vetting, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.
From the other side of the consultation, briefly. The version of this that has an answer is narrower than the version being asked. Narrow it and it becomes tractable; leave it broad and the thread will produce nine confident and incompatible replies.
JenPlateau said:The version of this that has an answer is narrower than the version being asked.
Agreed, with a caveat about community reputation: it is a lagging indicator. Reports arrive weeks after orders, so a supplier can look excellent for a month after quality has already changed.
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Browse GL BiochemJenPlateau said:The version of this that has an answer is narrower than the version being asked.
There is a second half to this that has not been said yet. The useful checklist is about verifiability rather than presentation. Independent test results commissioned by buyers rather than by the seller, consistency across multiple batches over time rather than one flattering report, a physical address and a company registration that resolve, batch and lot numbers on the actual labelling, and a shipping practice that matches what the material needs. Everything a good-looking website provides is cheap to fake; none of the items above are.
Moderator note: good thread. Keeping it here rather than moving it, because the question is general enough to be useful. No action needed from anybody.