It's literally the same as you getting blood drawn. Takes less than a minute and the only part that hurts is when they initially put the needle in.

Have a snack or his favorite toy handy to help soothe him when they're done.

It’s the same as when you get one ... nothing to worry about ... your child will go off of you

So if your not up to that you might want to take someone that can do it ... also ask for the best person they have that is good at doing it to small children because I can guarantee you that there is one .... I work in a clinic and I see it all the time