How often is blood test needed for child on tegretol?

Probably often early: In adults, because of adverse affects, like temporary loss of blood platelets, blood testing is done frequently during the first few months, and them 3-4 times a year. It is important to know that stable concentrations of this drug are attained 2 to 3 weeks after it is started. Being that this is a child, the dosage and testing may be different but similar. See your doctor for details.