"Consumer and scientific groups have for years urged the Food and Drug Administration to make companies disclose caffeine levels, but the agency says it lacks the authority. Bottom line. Caffeine can make you feel more alert, boost your mental and physical performance, and even elevate your mood. But it can also make you jittery, keep you from sleeping, cause rapid pulse or abnormal heart rhythms, and raise blood pressure. Safe limits of caffeine consumption are still being studied, but data suggest that most healthy adults can safely consume up to 400 milligrams per day; pregnant women, up to 200 milligrams; and children, up to 45 to 85 milligrams depending on weight. An occasional energy drink is probably fine for most adults. Check the Ratings for caffeine levels and price. And note that some products cost less than half as much as others per serving." - Lit

I still vaguely remember the case with the HGV driver who drank ~15 red-bulls and then caused him to trip and he caused a high speed police chase down the motor way as he was too high, all he was trying to do was keep awake. Having said that, I'm not even sure if this is a true story or an urban myth now? - Halil