A fentanyl overdose may result in signs and symptoms such as:
stupor (dazed or nearly unconscious)
coma (cannot be awakened, unable to speak)
pupil constriction
slowed or absent breathing (respiratory depression or failure)
cyanosis (bluish or purplish tint to the skin, lips or fingernails due to low oxygen levels)
vomiting
heartbeat slows or stops
death