HPLC_Greg said:

The pattern that distinguishes a bad batch from an exit is behaviour rather than product.

I disagree that testing history is decisive. It tells you what a supplier did when they were being watched. Continuity of behaviour under stress — a late shipment, a failed test, a complaint — is more predictive than any run of good results.

tyler_CSCS said:

Six orders from the same supplier over eight months, every one independently tested, and the consistency is the part worth reporting rather than any…

Vendor reputation tracking for vendor vetting: I maintain a personal spreadsheet with every order I've placed — date, vendor, batch number, Janoshik result, personal efficacy assessment (1-5 scale), and any issues.

After 19 orders across 4 vendors: average purity 98.7%, zero sterility concerns, 2 shipping issues (all resolved). This data gives me confidence in my current source and documentation if issues arise.

I encourage everyone to track their orders systematically. Community data aggregation makes us all safer.

SarahChen_PharmD said:

I disagree that testing history is decisive.

There is a second half to this that has not been said yet. It is worth asking what the claim would look like if it were false. If nothing would look different, it is not a claim about the world and no amount of discussion will settle it.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

One thing that is still open after traveltech_sara’s answer:

What a vetting checklist should actually contain, as opposed to a list of things that are easy to fake?

Reporting back.

Went back through my own correspondence with an earlier supplier and the warning signs were all there in the replies, weeks before the quality changed. I was reading the product and not the behaviour.