My bests friends son needs growth hormone injections every night and her little girl will be starting them soon as well. He stopped growing at 6 months and after a year of tests, they confirmed he would need it. He grew 7 inches in one year! He gets it in the subcuntaneuos area of his thing, he doesn't like them in his bum. The needle is so small, it doesn't even seem to phase him. We call it his grow big and he knows it's part of his day. He used to fuss, but i think it was more of a over dramatic tanttrum, then actual pain. He now brags about it and likes to get it done in front of his friends to show how brave he is. He started them a little before he turned 3 and is now almost 7. He has grown almost enough to be in the normal range for height. He will get to keep takng it until he is a height that he is comfortable with. When the little one, the girl, starts takig it, I'm sure she will cry a bit at first, but for the most part, if we are matter of fact with her and tell her that we have to do this and we know she doesn't like it. Then offer a reward of sorts, maybe a sticker or favorite TV show time as first. Eventually it will just be part of her bedtime routine. Best of luck, you will both become experts at it and your child will get to grow and be healthy as a result.