Yes is important to get a good realistic reading, cats get used to changes especially food changes, she might give you a hard time, but you want to know how the insulin is working throughout the day and in-between, you can trick her at testing time, give her just one ONE! kibble just before you prick, for association, but only a couple of test don’t get her used to it, then while she’s feeding and has her face in the bowl pick up the scruff just below the head, careful, pick it up well, then while she’s bone is close by , shoot straight down always, to avoid a fur shot, if you get a fur shot, we all do at one time or another, do not shoot again, there’s a possibility that some insulin when in, you just wait for the next shot, this is to avoid a hypoglycemia episode