Because lithium levels required for therapeutic effectiveness are very close to toxic levels, overdose is a serious risk. Intake of plenty of water helps prevent toxicity. Signs and symptoms of overdose require immediate medical attention and discontinuation of lithium. In many cases, dialysis is required for several weeks.

Symptoms of mild to moderate lithium overdose include:

• Vomiting
• Abdominal pain
• Dry mouth
• Lack of coordination
• Dizziness
• Slurred speech
• Rapid, involuntary eye movements (nystagmus)
• Lethargy or excitement
• Muscle weakness

Symptoms of moderate to severe lithium overdose include:

• Loss of appetite (anorexia)
• Persistent nausea and vomiting
• Blurred vision
• Visible muscle twitching
• Rapid, abnormal limb movements
• Seizures
• Delirium
• Fainting
• Stupor
• Hypotension (low blood pressure)
• Cardiac arrhythmias (irregular heart beat)
• Coma

Overdose of anticonvulsant mood stabilizers is also dangerous and can lead to coma or death. Common symptoms include:

• Nausea
• Vomiting
• Drowsiness
• Confusion
• Over- or underactive reflexes
• Seizures
• Trouble breathing