Depends on what else you have tried. If you've altered his diet, if he gets 10-11 hours of sleep at night, and if he gets at least 30 minutes of good exercise at least 3 days a week and none of that works, then medication might be the next step. But try the 3 things I mentioned first, that might be all he needs. I don't have time to post about a good diet for ADD kids, but you can look at my other hundred billion posts on the subject. I have a now 7 year old daughter who I am pretty sure has ADD, and when she was around 5 years old, I did the three things I mentioned and it's amazing the difference it made. I also now have her taking a supplement called Attentive Child, which also made a world of difference in her school work.
(sorry this is kind of scattered, I have a screaming baby distracting me right now!)