It can be hard to tell how much caffeine energy drinks contain. Consumer Reports has just conducted lab tests on dozens of top-selling drinks.
Celebrities from Tim Tebow to 50 Cent and Joan Rivers are advertising energy drinks. With their Facebook pages and internet video campaigns, manufacturers specifically target young people.
But Consumer Reports says you have to be careful how much caffeine you drink.
"It can quicken your pulse, cause abnormal heart rhythms, keep you from sleeping well and elevate your blood pressure," said Gayle Williams of Consumer Reports.
Consumer Reports analyzed the caffeine content of 27 top-selling energy drinks. Companies are not required to list the content on their packaging. Of the 16 that did, Consumer Reports found the numbers were off on about a third of them.
"Some of the energy drinks underestimated the amount of caffeine listed on the label by 20 percent or more," said Williams.
So how much caffeine do energy drinks contain? In Consumer Reports' tests, it varied widely.
For example, FRS Healthy Energy averaged 17 milligrams per container; Red Bull and Street King Energy around 80. 5-Hour Energy - 215 milligrams and 5-hour Energy Extra Strength - 242. Most healthy adults can consume up to 400 milligrams of caffeine a day.
"So for many people, an occasional energy drink is probably okay," said Williams.
Or you can drink regular coffee. an eight-ounce cup contains roughly 100 milligrams of caffeine.
Consumer and scientific groups have urged the food and drug administration to require companies to disclose caffeine levels, but the agency says it lacks the authority to do so. Many energy drinks do carry warnings that they are not for children, women who are pregnant or nursing women, or people sensitive to caffeine.