Phenytoin, (brand name- Dilantin), is an anticonvulsant drug that is taken to control the occurrence of a plausible seizure after a surgery. The drug is usually consumed regularly as a mode of seizure control. The drug usually diminishes brain cell activities and hence its concentration in the body needs to be monitored. A high concentration can cause drop in blood pressure, a low concentration may fail in preventing seizure, and side effects include liver and kidney damage. Hence, a Phenytoin Blood Test is conducted to determine the concentration of phenytoin in blood and to ascertain that the level of the drug is within the acceptable range.