My 5 yo son has hgb of 11 at his 4 and 5 year check up. gave him mvi (multivitamin) w/iron & didn't help. rest of cbc wnl. he his having iron labs done. serious?

Slightly low: Hemoglobin for a five year old boy is usually 11.5 or more; try to find a cause if it's low. I trust he eats sensibly -- especially, that you aren't non-supplementing vegetarians. If the red cells are not low, Junior may have thalassemia minor, a non-problem that becomes important only if he plans to marry someone else who has the same thing. Ask your physician. It's quite common.