I Know how it is to take your child in  for bloodwork and have the lab nurse sweating buckets because she can’t find the vein, when our son was a baby he was quite chubby :).. and finding his veins was a job in itself, once they would find them he’d move his arm, or hand just a fraction and they would dissappear... I can remember on several occasions the lab would stick and stick and stick again and then go get someone else to try.. Oy!  But then our Endo gave us a prescription for  EMLA Cream.  You apply it about a half an hour to an hour before the blood draw is to be done, ..enough for about the size of a quarter, and cover it with a square plastic adhesive that comes with the cream, It was an entirely new experience after that, and I still use it today, also I’ve noticed that after using the cream they find his veins within a just a couple pokes of there finger.. It’s main ingredients are lidocaine, and prilocaine..  It comes in 5 gram tubes, ...I did try it on myself to be sure it didnt do anything weird, lol, the numbness last for about an hour after the plastic adhesive is taken off ot it.  Jacob has never had a skin irritation, or reaction from it but all kids are different..Be sure to ask your Endo about it.