Temperature-loss calculator
Left a vial on the counter overnight? Parcel sat in a hot van? Say what state it was in, how warm it got and for how long, and get an estimate of how much potency is likely left, and a plain verdict: fine, use soon, or replace.
What this does: estimates potency lost to heat and time, for dry powder or a mixed vial, using the standard rule that peptides break down about 2.5 times faster for every 10 °C warmer. What it does not do: measure your vial, or tell you what to take. It is for deciding whether to keep, use or replace.
1 What state was it in?
Dry powder is far more forgiving than a mixed vial. Once water is in, the clock runs faster.
2 How warm did it get?
Not sure? Pick the warmest it could plausibly have been. Overestimating is the safe direction.
3 For how long?
4 How fragile is it? (optional)
Classes come from published stability ranges for each family, not from testing your vial. When in doubt, "typical".
—
How the estimate is made: a mixed vial in the fridge is treated as losing about 10% over the usual 28 days, and dry powder about 2% a year; those rates are scaled up 2.5× for every 10 °C warmer (the Q10 rule used in stability work), and "sturdy" or "fragile" halves or doubles them. It is an estimate for a keep-or-replace decision, not a measurement, and never advice about what to take. A vial that is cloudy, discoloured or has threads in it is a replace regardless of the number; see the cloudy-vial guide.
Common questions
Is a peptide ruined if it was left out overnight?
Usually not. A mixed vial at room temperature overnight loses a small percentage by this estimate; dry powder loses almost nothing. Put it back in the fridge and use it sooner rather than later. The exception is a vial that was warm for days, or one that has changed how it looks.
My order sat in a hot delivery van for three days. Is the powder still good?
Sealed dry powder is the forgiving form: even three days at 40 °C comes out with most of its potency by this estimate. Mix it, keep it cold, and use it within the normal window. If the seal was broken or the powder looks discoloured or clumped, that is a different matter.
Is the result exact?
No. It is a model built on published stability rules, not a test of your vial, and different peptides in the same family vary. Use it to decide between keep, use soon and replace, and trust your eyes over the number when the vial looks wrong.
What is the 28-day rule?
Bacteriostatic water keeps a mixed vial from growing bacteria for about 28 days after the first puncture; after that it should go regardless of potency. The bac water guide explains it.
The supplies this assumes you have
A fridge thermometer so you know your fridge is at 2–8 °C, a temperature logger if parcels or travel are a regular thing, a travel cooler for the journey, and labels with the date on. The storage guide and the cooling guide are the long versions.