Carbamazepine is a drug that is primarily used to treat certain seizure disorders (epilepsy) but is also prescribed to stabilize the moods of patients with bipolar disease and to help alleviate some types of nerve pain. It works by reducing abnormal electrical activity in the brain. This test is used to monitor the levels of Carbamazepine because the drug must be maintained within a narrow therapeutic range. If levels are too LOW, the patient may experience a recurrence of symptoms (seizures, mania, or pain). Too HIGH of a level, and the patient may experience increased toxic side effects.