JenPlateau said:

Dose-response modeling for tirzepatide: Emax model fitting to the STEP/SURMOUNT dose-finding data shows: Semaglutide: ED50 ≈ 0.6mg, Emax ≈ -18%, Hill…

Right, and one flattering data point from a group buy is not consistency. Consistency means separate batches, separately commissioned, over months.

Worth separating that from vendor vetting, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

HPLC_Greg said:

One habit that pays for itself: post the method alongside the number.

Adding the part of the answer the thread has not reached. The pattern that distinguishes a bad batch from an exit is behaviour rather than product. A bad batch comes with communication, a reshipment offer and a batch number. An exit comes with slower replies, pressure toward less reversible payment methods, sudden discounting, and the same reassurance repeated without any new information. The product tells you less than the correspondence does.

Worth separating that from vendor vetting, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

One concrete data point for the thread. Keep the original post as written when you update it, and add the correction underneath. An edited-away mistake is invisible to the next person who makes it.

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

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

Moderator note: the sourcing question belongs in the vendor section and has been split out. Thread quality here is what the rules are for. Keep it up.