We bought this as our preworkout, a bit nervous about the side effects that may occur. We tried 1/2 scoop first and felt great, no tingles or rapid heartbeat, no sour stomach, just energized and focused. We went up to 1 whole scoop which did make me feel a bit tingly, so I opted to stay at 3/4 scoop, while my spouse does 1 whole scoop. It's been great and helps me feel energized for my workout and there's no crash afterwards. Love this product