It is very important to be taking a good multivitamin. You never want your body to be depleted of anything it needs and a multivitamin will help to ensure this doesn't happen. As far as when to take it, I think whatever works for you is fine. Just be consistent with taking it because taking it once every few days will not do the trick especially if you are dieting or working out. They have a lot of vitamin drinks out now too, but it is hard to find one without the sugar and additives that I don't need. I take a multivitamin daily and I can feel the difference from when I didn't take one.