@matigo I read an article on Apple News just a few hours ago on the subject of "caffeine overdose." Such deaths are rare, to put it simply. You need to have at least 5 grams of caffeine (some experts say 10 grams) to OD on the stuff. That 5 gram figure apparently equates to 6 gallon of McDonalds "coffee."
http://www.popsci.com/science/article/2012-10/fyi-how-much-caffeine-would-it-take-kill-you