Ashwagandha is probably safe if used for about 3 months. The safety of the long-term use of ashwagandha is not yet known. Overdose of ashwagandha can cause stomach upset, diarrhea, and vomiting. In addition, liver problems may occur, including severe liver failure and the need for liver transplantation. Therefore it is not positive to consume it for a long time without the advice of an expert.