Yes 68 is the absolute lowest you want him to go HOWEVER, don't aim for anything less than 80 to 90 because Vetsulin can cause swift drops in BG. While 68 still leaves a little cushion to bring BG back up a bit before you are potentially facing a true hypo situation with longer lasting insulins, a little more caution is needed with a fast acting insulin. So what this means is that if you get Tyler's BG and he is at 90 or lower, you should intervene with a little food to keep/get his BG up and stop him from dropping any further. If he is below 80 then I'd suggest using food in the medium carb range. If he is around 68, then high carb. If he's between 80 and 90 low carb to keep him surfing rather than trying to pump him up at all.