There is such a thing as too much caffeine. According to the FDA, they recommend individuals consume about 400 milligrams a day (about 4-5 cups of coffee). Of course, this amount will vary between each individual. Some may find that they need to consume less or none at all. Meanwhile, others are okay with consuming more caffeine. It all depends on someone's sensitivity and how their body metabolizes caffeine. However, if you find yourself experiencing any adverse side effects- it may be a sign that you need to cut back.
The FDA also estimates that 1,200mg of caffeine can lead to toxic effects. They also warn that caffeine in powder or liquid form can easily lead to ingestion of toxic levels. About one teaspoon of powdered caffeine equals about 28 cups of coffee. This amount may lead to health issues or even death.