I know nursing and medicine is a very trusting profession in general, but considering how lethal insulin can be, and how little it takes to do some real damage, it blows my mind that it's not a controlled drug.
It’s about logistics really. In many areas insulin is such a commonly used medicine that it would be an absolute nightmare for nurses to have to get a colleague to double sign every time they needed to use it. I used to work on a ward where most of our 32 patient at any one time would be on it, we would spend nearly all of our time signing and checking if we had to do that. Not to mention that most of the time in adult medicine, adults bring their own insulin pens in and it’s best practice to let them administer it themselves so they keep some control and don’t become complacent. If we had to take everyone’s insulin pens off them and put them in the CD cupboards many people, particularly type 1 diabetics who are used to controlling their own diabetes often very strictly, would kick off.
Also there’s no reason to want to steal it except to try and kill someone else or yourself - its not like you can get high off it.
Also it needs to be kept in the fridge if it’s a vial, or if it’s a pen kept in the fridge until someone starts to use it - therefore it couldn’t be kept with all the other CD medication.
You are supposed to get it checked by another nurse before giving it as even a slight miscalculation, or giving someone the wrong type of insulin, could be fatal or at least dangerous, but unfortunately in a busy ward that’s not always adhered to. But a nurse wouldn’t stand a chance in court or in front of the NMC if they made a mistake with insulin and didn’t get a second checker.