Creatine supplements are available over the counter, and teens make up a large portion of the supplement's users.

People who take creatine usually take it to improve strength, but the long-term and short-term effects of creatine use haven't been studied in teens and kids. Research in adults found that creatine is most effective for athletes doing intermittent high-intensity exercise with short recovery intervals, such as sprinting and power lifting.

However, researchers found no effect on athletic performance in nearly a third of athletes studied. Creatine has not been found to increase endurance or improve aerobic performance.

The most common side effects of creatine supplements include weight gain, diarrhea, abdominal pain, and muscle cramps. People with kidney problems should not use creatine because it may affect kidney function.

If you are considering using creatine, talk with your doctor about the risks and benefits, as well as appropriate dosing.