I think when the liver releases a huge amount of bile and toxins, it makes you nauseous. My first one, I vomited and had the most stones I've ever had in my 9 flsuhes, over 250. My last one I vomited, and only had 12 stones, but one huge one, and tons of bile and I felt so good for 2 weeks afterward. As long as you can keep it down the first 20 minutes, it has done its job. So don't despair!