Sorry for Ur friend but were usually talking about people who want 10iu and do 100iu or want 8iu and do 80iu.Happen to someone I knew he was new to diabetes but fucked up on his dosage and they found him dead.
To me a VERY VERY easy way to prevent this is to buy the tiny 0.3mL slin pins. Then if you need 8iu you can't possibly fuck it up. Unless u needed 3iu and accidently did 30iu but I'd Think most people could make it thru that with high glycemic foods.