I have done it too, yes, sometimes. But I have a close colleague who always does it after - and always forgets, so it's often over an hour before he realises he feels terrible. I have a bad short term memory so if I'm going to do that, once again I get the needle on the pen, put it right next to me, and write down how many units I'm meant to inject. I wouldn't do it regularly because I know I'd also end up regularly forgetting. I think for a newbie though, getting into a good routine with it is a good idea.