I noticed a difference right away. The Fatigued to Fantastic Daily Energy B Complex doesn't rev you up like caffeine, just provides a steady stream of energy throughout the day. I am a stay-at-home mom with 2 Autistic children, and I started taking this when I was having trouble sleeping. I noticed that, even with a lack of sleep, I had more energy and felt calmer. (I've since started taking the Revitalizing Sleep Formula periodically, and that works well, too.) I'm a bit of a cynic when it comes to supplements, but I highly recommend these.