Short term effects

Individual responses to caffeine vary, and these drinks should be consumed with caution because of how concentrated and potent they are. Energy drinks' stimulating properties can increase heart rate (sometimes to the point of palpitations) and blood pressure, lead to nausea and vomiting, cause convulsions, disturb sleep patterns or cause restlessness, anxiety, or agitation, and, in some cases, even death.

Additionally, energy drinks should not be used while exercising as the combination of fluid loss from sweating and the diuretic (water expelling) effect of the caffeine can leave you severely dehydrated.