Safe? The debate still wages on that. Most of the supplements on the market are designed for fully grown fully developed adults - not for kids in puberty. Puberty has caused a great deal of chemicals to be released into your blood stream causing changes in your body. Creatine is a naturally occurring substance in your body - since you are going through development at a very fast pace (puberty) tinkering or tampering with those chemicals could lead to problems later in life. Creatine is still a relatively 'new' supplement. Meaning that it has not been out there long enough to get a decent understanding of its potential long term effects. http://www.creatinemonohydrate.net/creatine_newsletter_1.html Scroll down to the Age Part for: How old do I need to be to take creatine? I commonly advise that you wait until after puberty to start taking creatine. This is only a precautionary suggestion since the long term consequences of creatine supplementation aren't well understood. In other words, if negative consequences of creatine supplementation do exist, then the younger you start taking creatine, the more likely they are to manifest during your lifetime. Furthermore, some studies have failed to show a clear effect of creatine on adolescent subjects, suggesting that creatine may be less effective in adolescents. Finally, athletes generally take creatine to enhance their performance during high intensity efforts. Therefore, a more pertinent question might be whether it is advisable for children to push themselves to such an extreme. There are those that believe that excessive force/stress might be harmful for a rapidly growing body. For example, placing too much stress on developing bones might alter bone growth and tendon development. Therefore, it may be inappropriate for children to exert themselves beyond the normal limits of play, making creatine use a mute point from the onset.

creatine is found in steak, so no it's not a steroid, 15 year should not take creatine as creatine is high sodium content and will give him a bloated look, not a good thing, but creatine will not kill him.