10 year old boy is not anemic,normal blood work but high esr at 30? what causes it? should we be concerned? what other tests shall we ask the doctor?

Stop worrying: ESR is a famously unreliable test, useful only when it's quite far from the reference range and in a few clinical settings. If Junior seems well, I wouldn't even have ordered it. If this was my own son, I wouldn't give this a second thought. Junior's lucky to have caring parents like you.

Elevated ESR: Why was ESR test done ? Does he have any joint pains Or any inflammation in any part of his body? Does he have recurrent tonsillitis or any other infection? any symptoms? Elevated ESR is a none spicific test it only indicates that some inflammatory process is going on, talk to his pediatrician about it, why it was done, have it repeated in 3 mos. If he is asymptomatic, don't worry. Good luck