How much caffeine is too much caffeine?
To overdose on caffeine, you'd probably have to drink around 75 8oz cups of brewed coffee over the course of just a few hours. The effects vary from person to person, but that's a good estimate for a toxic dose. On the other hand, it doesn't take much caffeine at all to start experiencing negative side-effects, like heart palpitations or mood swings. A review of 200 studies suggests that a safe dose for an adult is only about 3 8oz cups.