Thank you The GLP Lounge for vetting these vendors — saved me

Taking the question as asked, rather than the general version of it. 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.

I would rather be corrected than agreed with, if it comes to it.

MikeFit_NJ said:

The useful checklist is about verifiability rather than presentation.

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

tammy_FL said:

Eight months with one supplier, then a change in how they communicate that I noticed before I noticed anything about the product.

Same position here, arrived at the long way round. Prices dramatically below market are the strongest single signal, and the reason is arithmetic rather than suspicion. Synthesis, testing, and cold-chain shipping have floors. A price well under the floor means something was skipped, and the two things that get skipped are testing and content.

Adding the clinical framing, because it changes how the question reads.

Shipping damage protocol for vendor vetting orders: if your package arrives with visible damage, temperature excursion, or broken vials:

• Photograph EVERYTHING before discarding packaging
• Note the temperature of the cold pack (liquid = possibly too warm)
• Contact the vendor within 24 hours with photos
• Request a replacement shipment or refund
• Do NOT use potentially compromised medication

Reputable vendors will replace damaged shipments without argument. If they push back, that's a red flag about the vendor.