Accepted answer
Five days at 2–8 °C is about 5 refrigerated days of equivalent exposure. 2–8 °C is the condition the rule of thumb is anchored to, so it is the baseline rather than a multiplier: everything else in this thread is quoted relative to it. At 5 equivalent days a test is more likely to reassure you than to tell you something, which is a legitimate reason to run it and a poor reason to expect a finding. Either way, record the five days and the temperature now, while you still know them; an excursion you did not write down is an excursion you cannot interpret later.
Start with the physical state, because it changes the answer completely and is the first thing to establish.
That is the argument for shipping lyophilised rather than for shipping colder. A dry powder with low residual moisture is stable at ambient for months; the pathways that matter need water.
A single-use temperature logger costs a few pounds, records the whole journey and converts an argument into a record. If the history matters, this is the answer.
Single-use temperature loggers are standard practice in supply chains where temperature genuinely matters and are inexpensive at parcel scale.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Solutions are a different question and deserve the worry the solids get.
8Is there a reason to prefer minus eighty here, or is minus twenty genuinely enough? – Dr_Bram_Verhoeven 2 months ago add a comment