Everyone is different. They warn about a possible warm rush when you first take it which is because of one of the ingredients, but it doesn't last long. Heart palpitations can happen and blood pressure can increase. The side effects are minimal, at least for myself and I found that drinking half of a bottle to start is usually the best way to avoid those symptoms. My best advice is that, you know your body better than anyone and if you are nervous about taking this product, ask your doctor or pharmacist. Best of luck!