PeptideChemSF said:

Freezing is the one to avoid, and freeze-thaw more so.

Cold chain shipping for storage and cold: my last order arrived with the cold pack completely melted and the vial at room temperature. I contacted the vendor and they reshipped with better insulation.

What to look for in shipping: temperature monitoring strip inside package. If your peptide arrives warm, contact the vendor immediately. Don't assume it's still good.

Following on from Dr.RenalNash — and this may be the naive question:

What did you change at the same time, and can you separate the two now?

Dr.PulmRoch said:

Cold chain shipping for storage and cold: my last order arrived with the cold pack completely melted and the vial at room temperature.

Adding the part of the answer the thread has not reached. Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then measure again under the same conditions.

OP back with an update, since a thread like this is useless without one.

Follow-up — I binned the frozen one. Aggregation does not undo itself and I was not going to inject a maybe.

Dr.NutriCornell said:

Order of operations matters more than any single choice here: establish a baseline, change one thing, wait long enough for it to express itself, then…

Agreed, with the usual condition: that holds for the average and this board is a collection of individuals. A population claim and a personal prediction are different things and get quoted interchangeably.