> I know there are testing companies that will test certain sources but it’s not like they’ve tested the vial you get.

It's why you order a decent amount of it (e.g. 2 years supply, it lasts forever in a freezer) and pay for your own randomized testing of the batch you got. You go direct to the source, not via the middle men selling it for 10x markup on a per-vial basis.

Certainly not perfect, and it adds significant cost - but still way cheaper than the regular sources via pharmacy for Zepbound.

I'm not convinced reta really shows that greater of results than tirz though. YMMV significantly here. Tirz is already so effective you are chasing marginal gains for the most part.