A 12-ounce cola has 35 mg of caffeine, but some of the newest energy drinks contain 14 times moreenough caffeine to lead to anxiety, insomnia, dehydration, stomach woes, or a dangerously fast heartbeat in some people (and it could pose special dangers to pregnant women). The risks are so worrisome that Johns Hopkins University scientists who have spent decades researching the effects of caffeine are pushing for warning labels. They say it makes no sense that over-the-counter supplements like No-Doz (which has 200 mg) require warnings, yet energy drinks that may have much more caffeine dont. So how much caffeine are you really getting? Check our chart.