There are numerous types of white blood cells (WBC) that help fight infections in the body. A WBC differential is included in the lab testing and specifies the percentage of each subtype of WBCs are in the blood, also identifying any immature types which might malfunction. This WBC differential must be closely monitored for patients who are taking clozapine, and specifically the absolute neutrophil count (ANC). When the ANC drops below 1500, the patient has neutropenia, or insufficient neutrophils needed to fight infections. This leaves them at risk for infections such as pharyngitis (infected, sore throat), oral ulcers, peri-anal ulcerations, high fevers, and potentially life-threatening sepsis (when infection becomes widespread in the body/bloodstream and the immune system reacts strongly and out of safe balance).