From the FDA Drug Label
Following overdose, serum caffeine levels have ranged from approximately 24 mg/L (a post marketing spontaneous case report in which an infant exhibited irritability, poor feeding and insomnia) to 350 mg/L. Another case of caffeine citrate overdose (from New Zealand) of an estimated 600 mg caffeine citrate (approximately 322 mg/kg) administered over 40 minutes was complicated by tachycardia, ST depression, respiratory distress, heart failure, gastric distention, acidosis and a severe extravasation burn with tissue necrosis at the peripheral intravenous injection site No deaths associated with caffeine overdose have been reported in preterm infants.
The lethal dose for caffeine is not explicitly stated in the provided drug label. However, it is mentioned that no deaths associated with caffeine overdose have been reported in preterm infants, and a case of overdose with an estimated 600 mg caffeine citrate (approximately 322 mg/kg) resulted in severe complications but not death 1.
From the Research
The lethal dose of caffeine for adults is generally considered to be around 10 grams (10,000 mg) consumed at once, though fatal cases have occurred at lower doses around 5-10 grams, as reported in a case study where a 39-year-old man died after ingesting approximately 12 g of pure caffeine anhydrous 2. For context, a typical cup of coffee contains about 80-100 mg of caffeine, meaning someone would need to consume approximately 100-140 cups of coffee in a very short time to reach potentially lethal levels. Caffeine toxicity can begin at much lower doses, with serious side effects possible at 1-2 grams, and concentrations of 80-100 mg/L are considered lethal 3. Individuals with certain heart conditions, liver disease, or who take medications that interact with caffeine may be at risk from lower doses. Symptoms of caffeine overdose include severe vomiting, irregular heartbeat, seizures, and potentially death from cardiac arrhythmias. Children and people with lower body weights require significantly less caffeine to experience toxicity. The body metabolizes caffeine at approximately 50-100 mg per hour, so spreading consumption over time reduces risk compared to consuming large amounts rapidly. Some key points to consider include:
- Caffeine is a mild central nervous system stimulant that can be profoundly toxic in large doses, resulting in arrhythmia, tachycardia, vomiting, convulsions, coma, and death 4.
- Fatal caffeine overdoses in adults are relatively rare and require the ingestion of a large quantity of the drug, typically in excess of 5 g 4.
- Early identification and intervention with β-adrenergic antagonists and activated charcoal is paramount in caffeine toxicity, as reported in a case study where a 48-year-old lady survived a significant overdose of caffeine after receiving early treatment 5.
- Caffeine can increase seizure susceptibility and protect from seizures, depending on the dose, administration type, and the developmental stage at which caffeine exposure started, as reported in a systematic review and quantitative analysis 6.