Dr.NateNeph 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.

SandraNC_45 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 17 orders across 5 vendors: average purity 98.1%, zero sterility concerns, 0 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.

Dr.MetabolicMD said:

I disagree that testing history is decisive.

There is a second half to this that has not been said yet. There is a difference between no evidence and evidence of no effect, and this subject is one where the two get swapped freely in both directions.

That is the short version; the long version is somebody else's post.

Following on from MikeFit_NJ — and this may be the naive question:

How people are distinguishing a supplier having a bad batch from a supplier on the way out?

Closing the loop on my own question.

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.