Teen athletes often turn to energy drinks for a boost during physical activity — or for an added edge during competition. But be aware: Energy drinks are not designed to replace lost fluids during exercise. Rather than re-hydrating their bodies, these beverages may actually lead to dehydration.

It’s also important to be aware that some energy drinks have between 150-500 milligrams of caffeine in 8 ounces.  Unfortunately, the amount of caffeine is not often listed on the can. To provide a comparison on the caffeine content, 8 ounces of coffee has about 108 milligrams of caffeine, brewed tea has 50 milligrams and 12 ounces of coke has 34 milligrams. Take a look at this chart to find out the caffeine content in many popular energy drinks – and see the huge range that exists.

For more, listen to this related NPR story, The Buzz on Energy Drinks.