I tried this a few months ago after buying a sample pack and have since continued using it pretty much every morning. I don't necessarily "feel it working", but it does seem to me as though I am better focused and more ready to take on the day when I have a glass in the morning on the drive in. I've only tried the citrus flavor and the pink lemonade... not so much a fan of the lemonade but I'm on my 3rd jar of citrus.