So I was pleased to read this report in The New York Times that said for caffeine to be lethal, it would probably take a lot more than a few new Starbucks Trentas. According to the piece, you’d need to drink about 42 cups of coffee in one sitting to kill you.
Still, caffeine overdoses are not uncommon:
Concentrations of caffeine in blood plasma that are higher than 15 milligrams per liter of blood can cause toxic reactions, and caffeine overdoses are a relatively common cause of poisoning emergencies, with 4,183 such cases reported by the American Association of Poison Control Centers in 2007.Only one death occurred among those cases.
When caffeine does kill, the reported causes are abnormal heart rhythms, seizures and breathing in vomit.