The optimal dose for maximizing the chance that exercise performance will be enhanced is 3 – 6 mg/kg, where side effects are minimized and urine levels are legal. The side effects of caffeine ingestion include anxiety, jitters, inability to focus, gastrointestinal unrest, insomnia, irritability, and, with higher doses, the risk of heart arrhythmias and mild hallucinations. While the side effects associated with doses of up to 9 mg/kg do not appear to be dangerous, they can be disconcerting if present prior to a competition and may impair performance. Ingestion of higher doses of caffeine (10-15 mg/kg) is not recommended as the side effects worsen. It should also be noted that most studies have used pure caffeine rather than a caffeinated beverage or food. Thus, it is not certain that consuming the “equivalent dose of caffeine” as coffee, for example, will have the same result.