Hello Giancarlo,
Sorry it took so long to get back to you. Ginseng takes a little while to build up in your system before you really start noticing the results. For me it took at least a solid month before I could feel the effects, but it was well worth the wait. I continue to take it as a lifestyle medication, one pill every morning with breakfast. I believe that morning is the best time to take it, as this gives your body all day to process it. Taking with food is optimal in my opinion, although I do not miss a dosage if I am running late in the morning and don't have time to eat.
What I use is the 'Triple Ginseng' standardized formula from the GNC store in the mall.
I hope my response has been of some help to you. I urge you to try it for at least a month; you might be surprised at some of the unintended benefits (like how it took away my chronic heartburn.)