Is muscle milk ok to give to my 12 year old son. he is a very active athlete.

Protein: Muscle milk is just a high protein shake, with vitamins, minerals. If your son gets adequate protein from food, this is probably unnecessary. An athletic 12 year old is probably eating a lot. If his diet is balanced and healthy, he is in good shape. A bit more protein will not harm your son, but I tend to be concerned about what else may be in these shakes (read ingredients carefully).