I have been taking Zantrex3 for a few weeks now, though I took a break during the holidays. There is a large amount of Niacin in the product that many people react differently to. Your skin may feel red and itchy, especially your face and ears. I felt this a little in the beginning. I noticed that if I sat still, my heart would pound and at times I felt like I couldn\'t breathe. This too went away. I tell my friends that you have to be prepared to take it. Take it on days that you have a lot to do or need energy. At first, take it in small doses, starting with one pill a day and gradually take more if you can handle it and are getting sleep at night. I only take two in the morning and that\'s it. I have lost 12 lbs. total and I believe it would have been more if I would have continued to take it over the holiday season. No one knows your body but you and you have to see if it works for you, not anyone else.