Symptoms of caffeine intoxication include nausea, headache, heart palpitations, insomnia, anxiety or daily headaches.

The "boost" from energy drinks comes from the high levels of caffeine and sugar they contain. An 8.3oz, popular energy drink has 280mg of caffeine (about two to three cups of coffee). This represents a moderate, daily dose of caffeine, but when combined with other stimulants, especially alcohol, it can be dangerous.