NEW YORK — Between homework, cheerleading and working at Wendy's, Megan Ward was tired from being always on the go. So last year the 16-year-old began drinking a Red Bull or Monster energy drink before school and sometimes a second one before cheerleading practice.

"I was trying to get energy," says Megan, of Castle Rock, Colo. "In the morning, it gives me that extra boost to get me up and get me going. It wears off, and then I'm ready to go."

Energy drinks, laden with caffeine and sugar, have become the beverage of choice for many teens; 30 percent say they regularly drink them, according to a 2007 report from Mintel, a Chicago market research firm, up from 20 percent in 2002. That compares to just 14 percent of adults who say they drink them.

But while teens tout the coolness, energizing factor and taste, the popularity of energy drinks among young people has raised concern among medical professionals, schools and state and local officials, who are pushing to limit teens' access to the drinks.

At issue are the drinks' heavy caffeine and sugar content, the common practice of mixing them with alcohol, and advertising that seems to target minors for drinks with names like Cocaine.

Principals and teachers across the country are urging parents not to send their children to school with them. Legislators from Maine and Kentucky introduced bills this year banning the sale of highly caffeinated energy drinks to minors. (Neither passed.)

In Florida, Broward County schools considered a districtwide ban after four middle school students became sick from drinking energy drinks. A 16-year-old student in Palm Beach County, Fla., died last month after consuming alcohol and energy drinks, according to her family. Investigators were awaiting the results of a toxicology report.

The FDA does not have a formal limit on the amount of caffeine that can be in foods but says about 72 mg of caffeine is "generally recognized as safe" for cola-type beverages. An 8-ounce cup of coffee has anywhere from 75 to 300 mg, according to caffeine researcher Laura Juliano, a professor at American University.

Some energy drinks have as much as 500 mg for a 24-ounce can, and teens who drink them say they find themselves in a buzz-crash pattern.

"I can't get off them," says Greg Schubert, 16, of Nixa, Mo., who drinks two Monsters a day. "Whenever I don't have them, I feel tired and worn out. I try to cut down, but when I do I want more."

Energy drinks can impair children's sleep, make them jittery and add unwanted calories, says registered dietitian Joan Salge Blake. She adds that the drinks are displacing low-fat and skim milk, needed for calcium and Vitamin D.