In case of overdose, seek medical attention.

Symptoms of overdose may include:

• Fainting
• Drowsiness
• Fast heartbeat
• Dizziness

Most instances of acute overdosage result only in sedation, hypotension and tachycardia, but cardiac arrythmia, coma and death have occurred in adults. Serum or plasma quetiapine concentrations are usually in the 1–10 mg/L range in overdose survivors, while postmortem blood levels of 10–25 mg/L are generally observed in fatal cases.