Conditions: survodutide · minus 80 °C · five days.
I want to decide this in advance so that I am not deciding it under pressure later.
Assume I will follow the plan I write down, so I would like it to be a good one.
What would you do, and what would make you change course?
Five days at minus 80 °C. minus 80 °C is 85 kelvin below a refrigerator, and below the glass transition of a lyophilised cake the ten-degree rule of thumb stops applying at all — solid-state chemistry is not slow liquid chemistry, it is a different regime, and the failure modes that survive it are mechanical rather than chemical. The thing to establish is how many times it froze and thawed, not how long it sat: five days at one stable temperature is gentler than a single uncontrolled transition. 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.
The honest answer is that the cold pack is doing much less than people think and that shipping lyophilised is what actually protects the material.
Arrhenius behaviour means the degradation rate roughly doubles per ten degrees. A week at thirty degrees is therefore a meaningful exposure for a solution and an immaterial one for a dry solid.
Worth being precise here: a pack that arrived hard tells you about the last day of transit only, since it will have melted and, if the ambient dropped, partially refrozen.
Single-use temperature loggers are standard practice in supply chains where temperature genuinely matters and are inexpensive at parcel scale.
Solutions are a different question and deserve the worry the solids get.
Aggregated, published test results and vendor ratings built from submitted batches. Methodology stated, dataset browsable, no listing fees.
Browse resultsAnswering this needs the transit duration and the ambient temperature, and then the arithmetic is straightforward.
Once the parcel arrives, the domestic leg is the controllable part: get it into the refrigerator promptly rather than leaving it in a warm hallway for a day.
Stated carefully, asking a supplier to hold a shipment during a heatwave is reasonable and the better ones agree; the cost is a week and the benefit is a shorter warm exposure for anything in solution.
Phase-change pack hold time is a function of mass, latent heat and insulation, and published figures for small parcels are on the order of one to two days.
Lyophilised tolerates the lane. That is the answer for almost every order.
The relevant physics is latent heat: a phase-change pack holds temperature only while it is changing phase, and once it has melted it is a warm mass.
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.
Arrhenius kinetics predict approximately a doubling of degradation rate per ten-degree rise and are the standard basis for cold-chain design.
A liquefied pack is expected. It is not evidence of a problem.
It helps to be literal here: this is where the anxiety in this hobby is most out of proportion to the chemistry.
Anything shipped in solution is a different risk category, because hydrolysis and deamidation proceed in the aqueous phase and are strongly temperature-dependent.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Buy a logger if you actually want to know. Everything else is inference.
edited 12 Mar 2026 by Dr_Bram_Verhoeven — updated for the 2026 guidance change
Answer first: for a lyophilised solid the cold chain matters far less than people believe, and for a solution it matters far more than they act as though it does.
A single phase-change pack in a thin-walled box holds below ten degrees for roughly one to two days at twenty-five degrees ambient, and under a day at thirty-five. On a nine-to-fourteen-day lane the material is at ambient for most of the journey whatever was packed with it.
Reconstituted material has a genuine cold-chain requirement and it starts the moment water is added.
The domestic leg is the part you control. Refrigerate it promptly.
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