This sounds obvious but I always thought it was just the coldness
@Dairygrade
However, I do think some insulins sting more than others.
The first insulin that I took, it had to be stored in the fridge and kept there in between doses.
This really only lasted a day or so while we were looking for an appropriate drug. Unfortunately I don't recall its stinginess.
The second drug, which I still take, needs to be stored in the fridge, but once opened, can just be stored in gresh air (each pen lasts me about half a week).
So there could well be something in what you say,
@azure.
I must admit, though, I find a small amount of stinginess reassuring, because it tells me that everything went in ok.