My son 12yr has monocytes 10% n hemoglobin is 11.3. all other cbp is normal?

What prompted a CBC?: assuming your son is healthy in every other way an elevated monocyte count is not necessarily suspicious. His hemoglobin is a little low and would bear further evaluation. Is there a family history of blood disorders? Has he been fighting an infection recently?. Most likely his doctor will recommend reevaluation in a month or two.