Cordyceps is possibly safe for most people when take appropriately. However, Cordyceps might cause the immune system to become more active, which could increase the symptoms of auto-immune diseases, like MS, lupus, RA and others. If you have one of these conditions, it’s best to avoid using Cordyceps. Don’t use it during pregnancy and breast feeding because there is not enough reliable information about the safety of taking Cordyceps during this time. And also Cordyceps might slow blood clotting. Taking Cordyceps might increase the risk of bleeding in people with bleeding disorders and definitely stop using Cordyceps 2 weeks before any surgery because it might increase the risk of bleeding during surgery.