I am no expert my any means but I can tell you that I do have a 3.4 lb spayed female and just rescued a 8yo 2.07lb unspayed female. With the exception of the 8yo being too skinny- mine are both healthy but.....I am constantly worrying about them. Getting stepped on, jumping, playing with my other dogs, making sure they are eating enough, taking them for their shots, spaying, constantly watching for hawks and owls when they are outside, my kids friends coming over, etc. I did not set out to get a 'tiny' yorkie, but this is what I have been blessed with and would not change it, but the worry that I go through with these girls sometimes makes me crazy. I dont think I worried about my skin kids as much as these girls.