I took it to help me when I leveled out after losing 35 lbs. It became harder and harder for the weight to come off. I took it for 3 days and I didnt notice a change in heart rate, anxiety or restlessness and I don't consume caffeine, like ever. I ended up catching the flu 3 days in and ever since then I have not started taking it again. I give it to my bf everyday to help with his diabetes.