Side effects from ginseng are rare and typically occur when it is taken in very large doses. These side effects include headache, indigestion and insomnia. Other possible side effects include agitation, increased risk of bleeding and changes in blood pressure. Ginseng is known to lower blood sugar, so diabetics should start with small dosages and carefully monitor blood sugar levels while using ginseng.
Since ginseng can cause the immune system to become more active, do not take ginseng after an organ transplant or if you have been diagnosed with an auto-immue disease without first consulting a doctor. Consult a doctor before using ginseng if you have been diagnosed with a severe heart condition. It is not recommended to take ginseng during pregnancy or breast-feeding.