I had to have my darling Fluffy, a 10 year old ig, euthanized because of kidney failure. The vet gave her the shot, and it took about an hour for it to work. It was very sad. I held her in my neck the whole time. The vet stayed with me, and listened to me telling Fluffy stories. It still brings a tear to my eyes when I think about it, and it was 6 years ago.