I am on day 7 and have noticed a pretty good visual difference. I've thrown in a couple more reps per workout. My fiance also noticed my vascularity tonight. Could be the mix of NO2 Red with OEP though... Anyway, Great energy, a little jittery if taken on an empty stomach, (which is not a big deal as long as you eat or take a protein shake with almonds 30 minutes later) and I DO NOT crash which is HuGe!