If you’re drinking so much coffee that you get tremors, have sleeping problems, or feel stressed and uncomfortable, then obviously you’re drinking too much coffee. But in terms of effects on mortality or other health factors, for example, we don’t see any negative effects of consuming up to six cups of coffee a day. Keep in mind that our study and in most studies of coffee, a “cup” of coffee is an 8-ounce cup with 100 mg of caffeine, not the 16 ounces you would get in a grande coffee at a Starbucks, which has about 330 mg of caffeine.