At 12 month of age, they do a blood test to check for Anemia. This is standard procedure at this age.
As for checking for lead exposure... our Pediatrician gives us a form to fill out... then depending on that outcome, will either recommend a blood test or not. Perhaps, your Doc is wanting a blood test for your son because they suspect of lead exposure. I don't believe a Pediatrician would suggest unnecessary blood-work unless it were needed, especially at this age.
As for getting a blood-draw... well both my daughter and son had those for various reasons. My daughter had her blood-draw at 1 yrs. old for the standard anemia testing... and my son had several blood draws within the first couple weeks of his life because he had bad jaundice. It's fine... sure.... you should be referred to a lab or hospital that handles children. Ask for a "butterfly needle" (this is for children and is a smaller needle). Or, they prick the finger and drip the blood via capillary action into a blood sample container. There is also a cream that can be applied that numbs the epidermis. But, this is usually not necessary & I don't know if it can be applied to children... the blood draw only hurts when the needle goes in...then it's over pretty quickly.
I know it seems like a horridly painful event... but if it is necessary, then you DO need to do it. Mostly, you can sit and hold your child during the process and to keep them still... you can turn and look away if it is uncomfortable for you... or you just try and soothe you child and distract them, sing to them etc.
In actuality, for me at least, the thinking about it is more horrible than the actual event. The child won't be "damaged" from it... and they will cry... but, if it has to be done, it has to be done. Especially if it is for health concerns.
Again, make sure that this IS necessary to do, OR is it optional in your son's case. Each child and situation is different.
Good luck and all the best,
Susan