The carbamazepine level test is a quantitative measurement of the concentration of the drug carbamazepine (commercially known as Tegretol) in the blood serum. Carbamazepine is used as an anticonvulsant (to treat epilepsy), a mood stabilizer (in bipolar disorder), and to treat nerve pain. It has a narrow therapeutic range, numerous drug interactions, and can cause serious side effects at high doses. Therapeutic monitoring (TDM) of its levels is routine and essential.